Q1. A heavy wire is suspended from a rigid support and no load is attached at its free end. Is it under stress?
Q2. Define Poisson’s ratio?
Q3. Define shear strain?
Q4. Why are electric poles given hollow structure?
Q5. What is the value of bulk modulus for an incompressible liquid?
Q6. What is the value of Young’s modulus for a perfectly rigid body?
Q7. What is value of rigidity of a liquid?
Q8. When a rod clamped at one end is heated, is it strained? What will happen when it is clamped at both ends?
Q9. Steel is more elastic than rubber. Explain why?
Q10. An elastic wire is cut to half of its original length. How would it affect the maximum load that the wire can support?
Q11. The breaking force for a wire is F. What will be the breaking force for (a) two parallel wires of the same size? (b) for a single wire of double the thickness?
Q12. A cable is replaced by another of the same length and material but of twice the diameter?
(a) How does this affect the elongation under a given load?
(b) How many times will be the maximum load supported by the latter as compared to the former?
Q13.The length of a metallic wire is L1, when the tension in the wire is T1; and is L2, when the tension is T2. Find the original length of the wire.
Q14. When a weight W is hung from one end of a wire of length L (other end being fixed), the length of the wire increases by l. If the wire is passed over a pulley and two weights W each are hung at the two ends, what will be the total elongation in the wire?
Q15. Discuss the variation of strain with stress?
Q16. Derive an expression for the elastic potential energy of a wire under stress.
FLUIDS AT REST
Q1. The bag and suitcases are provided with broad handles. Explain why.
Q2. What is meant by 1 torr of pressure?
Q3. What is 1 atmospheric pressure?
Q4. In dropper water does not come out, unless rubber bulb is pressed. Why?
Q5.One small and one big piece of cork are pushed below the surface of water. Which will have greater tendency to rise swiftly?
Q6. A cork is floating in a water tube. What is the apparent weight of the cork?
Q7. Why it may be difficult to stop bleeding from a cut in the body at high altitudes?
Q8. To empty an oil tin, two holes are made. Why?
Q9. Straws are used to take soft drinks. Why?
Q10. Why it is difficult to walk barefooted on a road covered with edged pebbles?
Q11. A man is sitting in a boat, which is floating in a pond. If the man drinks some water from the pond, what will happen to the level of water in the pond?
Q12. A boat carrying a number of large stones is floating in a water tank. What will happen to the level of water in the tank, if the stones are unloaded into water?
Q13. Ice floats in water with about nine-tenths of its volume submerged. What is the fractional volume submerged for an iceberg floating on a fresh water lake of a (hypothetical) planet, whose gravity is ten times that of the earth?
Q14. What is the fractional volume submerged of an icecube in a pail of water placed in an enclosure which is freely falling under gravity?
Q15. A cubic body floats on mercury with a part of its volume below the surface. Will the fractional volume of the body immersed in the mercury increase or decrease, if a layer of water poured on the top of the mercury covers the body completely?
Q16. A vessel of water is placed on the floor of an elevator. Will the pressure at the bottom of the vessel change if the elevator goes up with uniform acceleration a?
Q17. Explain why an air bubble in water rises from bottom to top?
Q18. Why mercury is preferred over water as a barometric substance?
Q19. It hurts more when a bather walks over sharp rocks in shallow water than when he walks over them in deep water. Why?
Q20. A piece of cork is embedded into an ice block which floats in water. What will happen to the level of water when the ice melts?
Q21. State and prove Pascal’s law?
Q22. What is atmospheric pressure? How can it be measured in the laboratory?
Q23. State and explain Archimede’s principle. Also state the law of floatation.
HEAT AND THERMOMETRY
Q1. The temperature of human body as recorded by a clinical thermometer is 98.4°F. What will be the corresponding temperatures on centigrade and Kelvin scales. Ans. 36.77°C, 299.92K
Q2. A thermometer has wrong calibration. It reads the melting point of ice as -10°C. It reads 60°C in place of 50°C. Calculate the temperature of boiling point of water on this scale?
Q3. A block of ice is dropped into a well of water, both the ice and water being at 0°C. From what height must the ice fall in order that 10% of it may melt? Ans. 3430m
Q4. Calculate the temperature whose value is same on the Celsius and Fahrenheit scale?
Q5. A clock with a steel pendulum has a time period of 2sec. at 20°C. If the temperature of the clock rises to 30°C, what will be the gain or loss per day? Coefficient of linear expansion of steel is 1.2x10-5°C-1. Ans. Slow by 5.18 sec per day
Q6. Railway lines are laid with gaps to allow for expansion. If the gap between steel rails 66m long be 3.63cm at 10°C, then at what temperature will the lines just touch? Coefficient of linear expansion for steel=11x10-6°C-1. Ans. 60°C
Q7. A faulty thermometer reads 5°C in melting ice and 99°C in steam. Find the correct temperature in °F when the faulty thermometer reads 52°C. Ans. 122°F
Q8. An ungraduated thermometer of uniform bore is attached to a centimeter scale and is found to read 10.3cm in melting ice, 26.8cm in boiling water and 6.5cm in freezing mixture. Calculate the temperature of the freezing mixture. Ans. -23.03°C
Q9. A brass scale of barometer gives correct reading at 0°C. Coefficient of linear expansion of brass is 2.0x10-5°C-1. The barometer reads 75cm at 27°C. What is the atmospheric pressure at 27°C? Ans. 75.04cm
Q10. A 50cm long rod made of material X is joined to another rod of same length and diameter(0.3cm) and made of material Y. Calculate the change in length of this combination when temperature is raised from 30°C to240°C. Given coefficients of linear expansion of X and Y are 2.1x10-5°C-1 and 1.2x10-5°C-1 respectively. Ans. 0.346cm
Q1. What is dimensional formula of G?
Q2. What is weight of a body of mass 10kg at the centre of earth?
Q3. If the diameter of the earth becomes twice its present value but its mass remains unchanged, then how would be the weight of an object on the surface of earth be affected?
Q4. It is said that air friction increases the velocity of the satellite. Explain?
Q5. Earth is continuously pulling moon towards its centre. Why does not moon fall on to the earth?
Q7. Prove that the areal velocity of a planet around the sun is constant?
Q8. How the value of g changes with depth?
Q9. Find an expression for gravitational potential energy of a body?
Q10. Define escape velocity. Derive an expression for it. Does it depend on mass of the body?
Q11. Derive an expression for orbital velocity, time period and height of satellite above earth’s surface?
Q12. Discuss the effect of rotation of earth on acc. due to gravity?
LAWS OF MOTION
Q1. Two bodies of different mass m and M(>m) are falling from the same height. If the resistance offered by the air is same for both the bodies, then which body will reach the ground earlier ? Q2. When a body falls on the earth, the earth also moves up to meet it. But the motion of the earth is not noticeable. Explain why?
Q3. Define angle of repose?
Q4. State & prove
Q5. Define static friction, limiting friction and sliding friction?
Q6. It is easier to pull a lawn roller than to push it. Explain?
Q7. Show that the tangent of angle of banking is inversely proportional to the radius of the curved path?
Q8. Find the maximum velocity with which a vehicle can take a safe turn at the curved road without skidding?
Q9. What is impulse? Discuss its few applications. State and prove impulse- momentum theorem.
Q10.Discuss flight of rocket as a variable mass problem. Find an expression for velocity of the rocket, upthrust on the rocket and burnt out speed of the rocket.
Q1. Can an object said to be at rest as well as in motion at the same time?
Q2. Find an expression for average speed when an object covers unequal distances with different speeds?
Q3. Derive an expression for distance covered by a uniformly accelerated body during nth second of its motion?
Q4. State and explain parallelogram law of vector addition?
Q5. Define angular velocity and angular acceleration. Derive relations (i) v=rw (ii) a=rα
Q6. Show that the velocity with which a projectile hits the ground is same with which it was thrown?
Q7. Derive equations of motion by calculus method?
Q8. A projectile is fired with velocity u at an angle with the horizontal. Find expression for maximum height, time of flight and horizontal range. Also prove that the path of the projectile will be a parabola?
KINETIC THEORY OF GASES
Q1. Mention the limitations of Boyle’s law and Charle’s law? (1)
Q2. Why are gas laws not obeyed at low temperature and high pressure? (1)
Q3. At what temperature does all molecular motion cease? Explain. (1)
Q4. Is there any existence of a perfect gas? (1)
Q5. What is mean free path? (1)
Q6. What is the nature of curve obtained, when volume of an ideal gas is plotted against its absolute temperature at constant pressure? (1)
Q7. What is the nature of the curve obtained, when pressure versus reciprocal of volume is plotted for an ideal gas at constant temperature? (1)
Q8. Two vessels separately contain 500cm³ of hydrogen and 500cm³ of oxygen at N.T.P. Which will have larger number of molecules? Give reasons. (1)
Q9. Which gas molecules will possess higher value of r.m.s. velocity-oxygen or hydrogen? (1)
Q10. Two different gases have exactly the same temperature. Does it imply that their molecules have the same r.m.s. speeds? (1)
Q11. The pressure of the gas increases, when the gas is heated. Why? (1)
Q12. What is kinetic interpretation of temperature? (1)
Q13. A box contains equal number of molecules of hydrogen and oxygen. If there is a fine hole in the box then which gas will leak rapidly and why? (1)
Q14. What is degree of freedom? (1)
Q15. What is law of equipartition of energy? (1)
Q16. Is Boyle’s law violated when we blow air in a balloon while blowing, both pressure and volume of air in the balloon increase? (1)
Q17. If a stationary air container, suddenly begins to move with a high speed, will the temperature of air rise? Why? (1)
Q18. How does the perfume of agarbatti spread throughout the room even in still air? (1)
Q19. Sugar cube added to a cup of tea dissolves quickly when stirred. Why? (1)
Q20. Why temperature less than absolute zero is not possible? (2)
Q21. Explain the phenomenon of evaporation on the basis of kinetic theory of gases? (2)
Q22. Explain how evaporation causes cooling? (2)
Q23. At ordinary temperature, the gas molecules have very large speed,(=500m/s), how is that gas takes several seconds to diffuse through a room? (2)
Q24. Explain the phenomenon of escape of gases from the earth’s atmosphere? (2)
Q25. Why there is practically no atmosphere near the surface of moon? (2)
Q26. When a gas is suddenly compressed, temperature rises. Why? (2)
Q27. On driving the scooter for a long time, the air pressure in the tyres slightly increases. Why?
Q28. Two perfect gases A and B are at temperatures T1 and T2. If the number of molecules of the two gases are N1 and N2 and the masses of the molecules m1 and m2, find the resulting temperature, when the two gases are mixed. Assume that there is no loss of energy on mixing the two gases. (2)
Q29. Two vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains neon (monoatomic), the second contains chlorine (diatomic).
(a) Do the vessels contain equal number of respective molecules?
(b) Is the root mean squared speed of molecules the same in the two cases? If not, in which case is vrms greater? (2)
Q30. A vessel is filled with a mixture of two different gases. However, number of molecules per unit volume of the two gases in the mixture are same. (a) Will the mean kinetic energy per molecule of both the gases be equal? (b) Will the pressure exerted by the two gases be equal? (c) Will the r.m.s. speeds of the molecules of the two gases be equal? State with reasons. (3)
Q31. Derive an expression for mean free path of a molecule of a gas? (3)
Q32. What are basic assumptions of kinetic theory of gases? On their basis, derive an expression for the pressure exerted by an ideal gas. (5)
Q33. Derive the expression for most probable speed, average speed and r.m.s. speed? (5)
LAWS OF MOTION
Q1. A force of 5N gives a mass m1 an acceleration of 8m/s² and a mass m2 an acceleration of 24m/s². What acc. would it give if both the masses are tied together? Ans. 6m/s²
Q2. A stone of mass 5kg falls from the top of a cliff 50m high and buries 1m in sand. Find the average resistance offered by the sand and the time it takes to penetrate. Ans. 2450N
Q3. A balloon of mass M is rising up with an acc. a. Show that the fraction of weight of the balloon that must be detached in order to double its acc. is ma/(2a+g), assuming the upthrust of air to remain the same.
Q4. A pendulum is hanging from the ceiling of a car having an acc. ‘a’ w.r.t. the road. Find the angle made by the string with the vertical.
(ii) tension T2 in the bodies
(iii) the force
Q6. A rubber ball of mass 50g falls from a height of 1m and rebounds to a height of 50cm. Find the impulse and the average force between the ball and the ground, if the time during which they were in contact was 0.1s. Ans. 0.3778Ns
Q7. A bomb at rest explodes into three fragments of equal masses. Two fragments fly off at right angles to each other with velocity 9m/s and 12m/s respectively. Calculate the speed of the third fragment. Ans.15m/s
Q8. A bullet of mass 7g is fired into a block of metal weighing 7kg. The block is free to move. After the impact, the velocity of the bullet and block is 70cm/s. What is the initial velocity of the bullet? Ans.700.7m/s
Q9.A bomb is thrown in a horizontal direction with a velocity of 50m/s. It explodes into two parts of masses 6kg and 3kg. The heavier fragment continues to move in the horizontal direction with a velocity of 80m/s. Calculate the velocity of the lighter fragment. Ans.10m/s
Q10. A batsman deflects a ball by an angle 60° without changing its initial speed which is 54km/hr. What is the impulse imparted to the ball if its mass is 150gm. Ans. 3.89Ns
Q11. Two blocks of masses 6kg and 4kg are connected by a rope of mass 2kg are resting on frictionless surface. If a constant force of 60N is applied to 6kg block, find the acc. of the system and tension in the rope at points A,B and C.
Q12. A body of mass m is suspended by two strings making angles α and β with the horizontal. Find the tensions in the strings. Ans. mgCosβ/Sin(α+β), mgCosα/Sin(α+β)
Q13. A man weighs 70kg. He stands on a weighing machine in a lift, which is moving
(a) upwards with a uniform speed of 10m/s
(b) downwards with a uniform acceleration of 5m/s²
(c) upwards with a uniform acceleration of 5m/s².
What would be the readings on the scale in each case? What would be the reading, if the lift mechanism failed and it came down freely under gravity? Ans. 686N,336N,1036N,0
Q14. Two masses 7kg and 12kg are connected at the ends of a light inextensible string that passes over frictionless pulley. Find the acceleration of the masses and the tension in the string, when the masses are released. Ans. 2.58m/s²,86.66N
Q15. A bullet of mass 0.01kg is fired horizontally into a 4kg wooden block at rest on a horizontal surface. The coefficient of kinetic friction between the block and the surface is 0.25. The bullet remains embedded in the block and the combination moves 20m before coming to rest. What is the speed with which the bullet struck the block? Ans. 3969.7m/s
Q16. A motor car running at the rate of 7m/s can be stopped by its breaks in 10m. Prove that total resistance to the motion when brakes are on is 1/4th of the weight of the car.
Q17. A horizontal force of 1.2N is applied on a 1.5kg block, which rests on a horizontal surface. If the coefficient of friction is 0.3, find the acceleration produced in the block.
Q18. A 4kg block A is placed on 8kg block B which rests on a smooth table. A just slips on when a force of 12N is applied on A. What is the maximum horizontal force, F, required to make both A and B move together? Ans. 36N
Q19. A block of mass 2kg rests on a plane inclined at 30° with the horizontal. The coefficient of friction between the block and the surface is 0.7. What will be the frictional force acting on the block? Ans. 9.8N
Q20. A block slides down an inclined plane of slope angle θ with the constant velocity. It is then projected up the same plane with an initial velocity v. How far up the incline will it move? Ans. S=v ²/4gSinθ
. A projectile is projected horizontally with a velocity of 330m/s from the top of tower 80m high. How long will it take to strike the ground at the base of tower? With what velocity will it strike the ground? Ans. 4.04s,332.36m/s
2. Two tall buildings are 45m apart. With what velocity must a ball be thrown horizontally from a window 50m above the ground in one building so that it enters a window 5.9m above the ground in the other building? Ans. 15m/s
3. An aeroplane is flying horizontally at a height of 490m with a velocity of 360km/h. A bag containing ration is to be dropped to the jawans on the ground. How far from them should the bag be released so that it falls directly over them? Ans. 1km
4. A player kicks a football at an angle of 30° with the horizontal and with an initial velocity of 19.6m/s. A second player standing at a distance of 20m from the first and in the direction of kick, starts running to meet the ball, at the instant it is kicked. How far and how fast must he run in order to catch the ball before it hits the ground? Ans. 13.94m, 6.97m/s
5. A cricketer can throw a ball to a maximum horizontal distance of 100m. How much high above the ground can the cricketer throw the same ball? Ans. 50m
6. Prove that maximum horizontal range is 4 times the maximum height attained by a projectile projected in a required oblique direction.
7. A ball of mass m is thrown vertically upward. Another ball of mass 2m is thrown up making an angle Ө with vertical. Both of them stay in air for the same time. What is the ratio of their maximum heights? Ans.1
8. Find the range of ball, which when projected with a velocity of 29.4m/s just passes over a pole 4.9m high.
9. A boy wants to throw a letter wrapped over a stone to his friend across the street 40m wide. The boy’s window is 10m below the friend’s window. How should he throw the letter?
Ans. With a velocity of 31.3m/s at an angle 26.56° with horizontal
10. A stone is dropped from the window of a bus moving at 60km/h. If the window is 196cm high, find the distance along the track which the stone moves before striking the ground.
11. A bullet from the ground is just able to cross in a horizontal direction the top of a wall 50m away and 25m high. Find the velocity and direction of projection of bullet. Ans.31.304m/s,45°
12. Show that there are two values of time for same height during the course of flight of a projectile and the sum of times at which these heights are attained is equal to the total time of flight.
13. A ball is dropped into a well in which the water level is at a depth h below the top. If the speed of sound is v, then calculate the time after which the splash is heard. Ans. h(√2/gh +1/v)
14. Show that the range of a projectile for two angles α and β is same where α+β=90°.
15. A bullet is fired at an angle of 30° with horizontal hits the ground 3km away. By adjusting its angle of projection, can one hope to hit a target 4km away? Ans. Not possible
16. A hunter aims his gun and fires a bullet directly at a monkey on a tree. At the instant the bullet leaves the barrel of the gun, the monkey drops. Will the bullet hit the monkey?
17. A projectile is thrown at an angle ө and another at angle 90°-ө from the same point, both with velocities 98m/s. The second rises 110m higher than the first, find their individual heights.
Ans. 190m, 300m
18. From the top of a tower 156.8m high a projectile is projected with a velocity of 39.2m/s in a direction making an angle 30° with horizontal. Find the distance from the foot of tower where it strikes the ground and time taken to do so. Ans. 8s, 271.57m
Q1. Which part of the liquid is responsible for the phenomenon of surface tension? (1)
Q2. Surface tension of a liquid is independent of the area of the surface. Explain why? (1)
Q3. The paints and lubricating oils have low surface tension. Why? (1)
Q4. What shape does a liquid take when it weighs nothing? (1)
Q5. Oil is poured to calm sea waves. Explain why? (1)
Q6. Soap bubble bursts after some time. Why? (1)
Q7. A mercury barometer always reads less than actual pressure. Why? (1)
Q8. Teflon is coated on the surface of non-sticking pan. Explain why? (1)
Q9. Why are brick walls plastered with cement? (1)
Q10. The anticeptics used for cuts and wounds have low surface tension. Explain why? (1)
Q11. Can you decide whether a liquid will rise or get depressed in a capillary tube by observing the shape of the liquid meniscus? (1)
Q12. A small boat with wax sticking to its one end, when placed on water, starts moving. Explain why? (1)
Q13. Tea runs up into a cube of sugar when one of its corner is placed in it. Why? (1)
Q14. Why we prefer cotton clothes in summer? (1)
Q15. End of a glass tube becomes round on heating. Explain? (1)
Q16. A piece of chalk immersed into water emits bubbles in all directions. Why? (1)
Q17. How would you know if the barometric tube contains air or not in the space above mercury column? (1)
Q18. How a dental plate clinge to the roof of mouth? (1)
Q19. Kerosene oil spreads over the surface of water, whereas water does not spread over the surface of oil? (1)
Q20. Detergents should have small angles of contact. Explain why? (1)
Q21. Why it is difficult to introduce mercury in a capillary tube? (1)
Q22. In order to increase the surface area of a liquid, work has to be done. Is it against the law of conservation of energy? (2)
Q23. Water is depressed in a glass tube, whose bore is coated with paraffin wax. Explain why?
Q24. How the rise of a liquid is affected if the capillary tube is closed at its top end? (2)
Q25. Water can be poured into a bottle having narrow neck with the aid of a glass rod. Explain why? (2)
Q26. A large air bubble is formed at one end of a capillary tube and a small one at the other end. Which one will grow at the expense of the other? (2)
Q27. Why water gets depressed in a glass tube whose inner surface is coated with wax? (2)
Q28. Both liquids and gases are fluids, then why concept of surface tension is applicable to liquids only? (2)
Q29. Why when two or more drops of mercury are brought into contact, they form one drop? (2)
Q30. Two bamboo sticks floating on a water surface are parallel and close to each other. When a hot needle is touched between them to the water surface, the bamboo sticks fly apart. Why? (2)
Q31. When there is a thin layer of water between two glass plates there is a strong attraction between them. Why? Do the plates attract if there is a thin layer of mercury between them? (2)
Q32. Why does an iron needle float on clean water but it sinks when detergent is added to this water? (2)
Q33. A capillary tube is dipped in water vertically. It is long enough for the water to rise to the maximum height h in the tube. The length of the portion of tube immersed in water is l<h. The lower end of the tube is closed and then the tube is taken out and opened again. Will all the water flow out of the tube? Explain. (2)
VISCOSITY AND FLUID FLOW
Q1. What is coefficient of viscosity? (1)
Q2. Two flasks, one containing water and other glycerine are stirred rapidly and kept on the table. In which flask, will the liquid come to rest earlier than the other? (1)
Q3. If honey and water are dropped out of a tube separately, the honey comes out later than water. Why? (1)
Q4. The velocity of water in a river is less on the bank and large in the middle. Explain, why. (1)
Q5. Why is it that we need a constant driving force for maintenance of the flow of oil through pipe-lines in oil refineries? (1)
Q6. Write dimensional formula for coefficient of viscosity? (1)
Q7. Define one deca-poise? (1)
Q8. Hotter liquids flows speeder than cold ones. Explain why? (1)
Q9. Why machine parts are jammed in winter? (1)
Q10. Why high viscosity liquids are used as buffers in trains? (1)
Q11.In which liquid, the terminal velocity of an object will have lesser value-water or honey? (1)
Q12. What is a streamline? (1)
Q13. Define critical velocity? (1)
Q14. What is laminar flow? (1)
Q15. What is turbulent flow? (1)
Q16. Is viscosity also exhibited by solids? (1)
Q17. Water is coming out of a hole made in the wall of a tank filled with fresh water. If the size of the hole is increased, will the velocity of efflux of water change? Will the volume of water coming out per second change? (1)
Q18. What is the weight of a body, when it falls with terminal velocity through a viscous medium? (1)
Q19. When air is blown in between the two balls suspended from a string such that they do not touch other, the balls are attracted towards each other. Why? (1)
Q20. Why drops falling freely under gravity do not acquire very high speed? (1)
Q21. Why is the speed of the whirlwind in a tornado alarmingly high? (1)
Q22. Air bubble in a liquid rises up. Why? (1)
Q23. Why accumulation of snow on aeroplane wings reduce the dynamic lift? (1)
Q24. While watering a distant plant, a gardener partially closes the exit of the pipe by putting his finger on it. Why this results in the water streams going to a longer distance? (2)
Q25. Which one falls faster, a big raindrop or a small raindrop? (2)
Q26. Why upper surface of wings of an aeroplane are made convex upward and lower concave downwards? (2)
Q27. Why does the pressure decrease when water flowing in a broader pipe enters into a narrow pipe? (2)
Q28. How will the blood flow through a capillary blood vessel change when the radius contracts to one-third of its normal size? Assume that its length and pressure drop across the capillary do not change. Which law is involved in this question? (2)
Q29. Why does dust particles generally settle down in a closed room? (2)
Q30. Why two streamlines cannot cross each other? (2)
Q31. Why do the clouds float in air? (2)
Q32. Explain the action of a parachute in retarding free fall? (2)
Q33. The destructive effect of a tornado(twister) is greater near the centre of the disturbance than near the edge. Why? (2)
Q34. Why does a cloudy track form at the back of an aeroplane flying at a high altitude? (2)
Q35. An aeroplane runs for some distance on the runway, before taking off. Why? (2)
Q36. Why does a flag flutter, when strong winds blow on a certain day? (2)
Q1. Which properties of a medium are responsible for propagation of waves through it? (1)
Q2. Can transverse waves be produced in air? (1)
Q3. Which characteristics of the medium, determine the velocity of sound waves in a medium?
Q4. Sound is produced due to vibratory motion. But a vibrating pendulum does not produce sound. Why? (1)
Q5.What happens to the frequency of an alarm clock if it is placed in vacuum? (1)
Q6. An explosion occurs inside a lake. What type of waves are produced inside the water? (1)
Q7. If you set your watch by the sound of a distant siren, will it go fast or slow? (1)
Q8. What is the effect of increase of pressure on speed of sound in air? (1)
Q9. In which medium, do the sound waves travel faster-solids, liquids or gases? (1)
Q10. What is the nature of thermal changes in air, when a sound wave propagates through it? (1)
Q11. Explain, why there is usually a time interval between observing a flash and hearing a thunder? (1)
Q12. Sound can be heard at great distances after rainfall. Explain. (1)
Q13. We cannot hear echo in a small room. Explain why? (1)
Q14. Why are stationary waves so called? (1)
Q15. Beats will be produced when the difference of frequencies is below 10. Explain. (1)
Q16. Explain why sound travels faster in warm air than in cool air? (1)
Q17. Is it possible to detect the approach of a distant train by placing the ear very close to the railway line? Explain. (1)
Q18. Which property is common in all type of waves? (1)
Q19. When we throw a stone on the surface of water, waves travel out. From where these waves get energy? (1)
Q20. How will you show experimentally that there is a transfer of energy by the wave? (1)
Q21. What types of waves are possible in solids? (1)
Q22. What is the difference between wave velocity and particle velocity? (1)
Q23. Why transverse waves are produced only in solid and on the surface of liquid and not inside a liquid or a gas? (2)
Q24. Why longitudinal waves are produced in solids, liquids and also in gases? (2)
Q25. Why Laplace applied the correction to
Q26. What is echo? Show that for an echo to be heard the distance between the source and observer should be more than 17metres? (2)
Q27. What do you understand by reverberation and reverberation time? (2)
Q29. What are stationary waves? Derive an expression for the stationary wave. (3)
Q30. What are characteristics of stationary waves? Define nodes and antinodes? (3)
Q31. Distinguish between progressive and stationary waves? (3)
Q32. What are organ pipes? Show analytically that the ratio of the frequencies of first three harmonics in open pipe is 1:2:3? (3)
Q33. Show analytically that in the case of a closed organ pipe, the ratio of the frequencies of the harmonics is 1:3:5:7? (3)
Q34. What are beats? Prove that the number of beats per second is equal to the difference between the frequencies of the two superposing waves? (3)
Q35. What is Doppler effect? How are the apparent frequencies determined when there is relative motion between source and listener? (5)
Q36. What is the effect of (a) pressure (b) temperature (c) density (d) humidity and (e) the direction of the wind on the velocity of sound? (5)
Q1. What is the difference between cathode rays and β-rays?
Q2. Why are α-particles emitted rather than any proton or 2He³ nuclei?
Q3. Define radioactive decay constant.
Q4. What is artificial transmutation?
Q5. What is radioactivity?
Q6. What are thermal neutrons?
Q7. Define critical mass for nuclear chain reaction.
Q8. Define binding energy of the nucleus?
Q9. What is the name of the first reactor in
Q10. What do you mean by Q-value of a nuclear reaction?
Q11. Why do all electrons emitted during β-decay not have the same energy?
Q12. Why heavy water is preferred over ordinary water as a moderator in a nuclear reactor?
Q13. What are secondary neutrons?
Q14. Why is the ionising power of α-particle more than that of β-particle?
Q15. Why is a neutron preferred as a bombarding particle?
Q16. Heavy nuclei are unstable. Explain why?
Q17. Why all the three radioactive rays i.e. α, β and γ are emitted from a radioactive sample when a single radioactive sample follows a particular decay mode?
Q18. How are β-rays emitted from a nucleus, when it does not contain electrons?
Q19. Give the relation between 1 a.m.u. and MeV.
Q20. In heavy nuclei, the number of neutrons is more than number of protons. Explain why?
Q21. Why is it difficult to realise nuclear fusion terrestrially?
Q22. Define half-life and decay constant of radioactive element. Derive the expression for them.
Q23. What is radioactivity? State laws of radioactive decay. Show that radioactive decay is exponential in nature.
Q24. What is nuclear fusion? Explain, how such large amount of energy is produced inside sun through proton-neutron cycle and carbon-carbon cycle.
Q25. What do you mean by binding energy of nucleus? Obtain an expression for binding energy. How binding energy per nucleon explains the stability of nucleus?
Q26. What are radio-isotopes? Explain their uses.
Q27. Explain the possible cause of nuclear forces.
CHEMICAL EFFECTS OF CURRENT
1. Can A.C. be used for electrolysis?
2. Define electrochemical equivalent of a substance?
Q1. What do you mean by communication? (1)
Q2. Name the three basic units of any communication system? (1)
Q3. What is a transducer? Give one example. (1)
Q4. What is modulation? (1)
Q5. Define amplitude modulation?
Q6. What is modulation index? (1)
Q7. What do you mean by bandwidth?
Q8. What is frequency modulation? (1)
Q9. Give the expression for band width in AM transmission? (1)
Q10. What do you mean by frequency deviation? (1)
Q11. Give the expression for bandwidth in FM modulation? (1)
Q12. In FM, the modulation index increases, the band width decreases. Is it true? (1)
Q13. What is the importance of modulation index? (1)
Q14.What is demodulation? (1)
Q15. What do you mean by modem? (1)
Q16. What is sensitivity? (1)
Q17. Define selectivity of the receiver? (1)
Q18. What is a fax? (1)
Q19. What is noise? What are their types? (2)
Q20. The audio signal cannot be transmitted directly into the space. Why? (2)
Q21. A radio broadcast is transmitted using amplitude modulation at a carrier frequency of 680 kHz. Explain? (2)
Q22. What are the limitations of amplitude modulation? (2)
Q23. Write three advantages of frequency modulation over amplitude modulation? (2)
Q24. What are the advantages of AM over FM transmission? (2)
Q25. Why is FM signal less susceptible to noise than an AM signal? (2)
Q26. What mode of communication is employed for transmission of TV signals? Explain why TV transmission towers are usually made very high? (2)
Q27. Write the advantages of digital communication over the analog communication system? (2)
Q28. Derive an expression for the distance upto which the TV signals can directly be received from a TV tower of height ‘h’. (2)
Q29. Define amplitude modulation. Derive an equation for it? (3)
Q30. Briefly explain the following terms:
(i) Pulse-amplitude modulation(PAM), and (ii) Pulse-code modulation(PCM).
Give one reason, why pulse code modulation(PCM) is preferred in transmitting signals? (3)
Q31. Describe amplitude demodulator circuit? (3)
Q32. The maximum peak to peak voltage of an A.M. wave is 32mV and minimum peak to peak voltage is 4mV. Find the modulation index?
Q33. A T.V. tower has a height 100m. How much population is covered by T.V. broadcast if the average population density around the tower is 1000/km²?
Q34. A T.V. tower has a height of 80m. Find the radius of the circle within which the transmission can be observed. How much population is covered by the T.V. broadcast if the average population density around the tower is 800/km²?
Q35. A T.V. tower has a height of 150m. By how much the height of tower be increased to double its coverage range?
Q36. You are given three semiconductors: A, B and C with respective bandgaps of 3eV, 2eV and 1eV for use in a photodetector to detect λ=1400nm. Select the suitable semiconductor. Give reasons.
Q37. A 90 kHz carrier is amplitude modulated by the speech band of 300Hz to 3000Hz. Determine the range of (a) upper side band (b) lower side band.
Q38. A 75MHz carrier having an amplitude of 50V is modulated by a 3 kHz audio signal having an amplitude of 20V. Find: (a) modulation index and, (b) frequency spectrum of AM wave?
Q1. Name the metal which has lowest resistivity.
Q2. What is the order of resistance of human body?
Q3. What is the effect of temperature on the internal resistance of the battery?
Q4. Can Ohm’s law be used to calculate currents in various parts of a complicated circuit?
Q5. Manganin or
Q6. The connecting wires are made of copper. Why?
Q7. A storage battery is to be charged from a
Q8. How does the drift velocity of electrons in a metallic conductor vary with increase in temperature?
Q9. Bends in a rubber pipe reduce the flow of water through it. How would the bend in a metallic wire affect its electric resistance?
Q10. A low voltage supply from which one needs high currents must have very low internal resistance. Why?
Q11. A copper wire of resistivity ρ is stretched to reduce its diameter to half of its previous value. What is its new resistivity?
Q12. The flow of charged particles in a definite direction constitutes an electric current. Even then the current is a scalar quantity. Explain why?
Q13. A wire is carrying current. Is it charged?
Q14. When we switch the lamp on, it lights up instantaneously. Can we conclude from it that the drift velocity of the electrons is very high?
Q15. Is Ohm’s law a universal law?
Q16. A high voltage supply should have a very large internal resistance. Why?
Q17. Can Kirchhoff’s laws be used for both
Q18. What are the basic concepts on which Kirchhoff’s laws are based?
Q19. Of which material, a thermistor is made up?
Q20.Why is the meter bridge given this name?
Q21. Why the copper strips fitted on meter bridge are made thick?
Q22. Why is a potentiometer named so?
Q23. Why is a copper wire not used in potentiometer?
Q24. Why should the e.m.f. of the driver cell in the potentiometer experiment be greater than the e.m.f. of cell to be measured?
Q25. How does the sensitivity of a potentiometer depend upon its length?
Q26. State condition in which terminal voltage across a secondary cell is equal to its e.m.f.?
Q27. Under what condition terminal potential difference of a cell becomes greater than its e.m.f.?
Q28. Define the terms drift velocity and relaxation time. Establish the relation between them.
Q29. State and deduce Ohm’s law? Also deduce its microscopic form?
Q30. What do you mean by the resistance of a conductor? Show that resistance of a conductor is given by R=ml/ne²Aτ, where the symbols have their usual meanings.
Q31. Define resistivity of the material. State its SI unit. Discuss the variation of resistivity with temperature in case of (i) conductors (ii) semiconductors and (iii) insulators.
Q32. What are the uses of potentiometer? Discuss how the e.m.f.’s of cell can be compared with the potentiometer.
Q33. Define Kirchhoff’s laws? Using these laws derive Wheatstone bridge principle.
Q34. How the resistance of wire can be determined using meter bridge?
Q1. A current of 300mA is flowing through a filament. How many electrons pass through any cross-section of the filament per minute? Ans.1.125x1020
Q2. In hydrogen atom, an e’ moves in an orbit of radius 5.0x10-11m with a speed of 2.2x106m/s. Find the equivalent current. Ans. 12mA
Q3. (a) Estimate the average drift speed of conduction e’s in a copper wire of cross-sectional area 1.0x10-7m² carrying a current of 1.5A. Assume that each copper atom contributes roughly one conduction e’. The density of copper is 9x103kg/m³, and its atomic mass is 63.5g.
(b) Compare the drift speed obtained above with
(i) thermal speed of copper atoms at ordinary temperatures,
(ii) speed of e’s carrying the current and,
(iii) speed of propagation of electric field along the conductor which causes the drift motion.
Q4. A potential difference of 100V is applied to the ends of a copper wire 1m long. Calculate the average drift velocity of the e’s. Compare it with thermal velocity at 27°C(for copper, take conductivity σ=5.81x107Ω-1m-1 and number density n=8.53x1028m-3). Ans. 0.43m/s, 1.17x105m/s
Q5. A given wire having resistance R is stretched so as to reduce its diameter to half of its previous value. What will be the new resistance. Ans.16R
Q6. The resistance of a wire is Rohm. What will be its resistance if it is stretched to n times its original length? Ans. n²R
Q7. If a copper wire is stretched to make 0.1% longer, what is percentage change in its resistance?
Q8. A wire has a resistance of 32Ω. It is melted and drawn into a wire of half of its original length. Calculate the new resistance of wire. What is the percentage change in resistance? Ans. 8Ω, 75%
Q9. Two wires X and Y are of equal masses and of same material. The diameter of wire X is half the diameter of wire Y. If the resistance of wire is 24Ω, calculate the resistance of wire Y. Ans. 1.5Ω
Q10. A wire of uniform cross-section and length l has a resistance of 16Ω. It is cut into four equal parts. Each part is stretched uniformly to length l and all the four stretched parts are connected in parallel. Calculate the total resistance of the combination so formed. Ans. 16Ω
1. A thin prism of 5° angle gives a deviation of 3.2°. What is the refractive index of the material of the prism. Ans. 1.64
2. A prism of refractive index 3/2 is placed in water of refractive index 4/3. If the prism angle is 60°, calculate the angle of minimum deviation in water. Ans. 8°28´
3. The refractive indices of crown and flint glasses for violet and red light are 1.523, 1.513, 1.773 and 1.743 respectively. Find the dispersive power of the glasses.
Ans. 0.019, 0.04
4. A ray of light is inclined to one face of the prism at an angle of 60°. If angle of prism is 60° and the ray is deviated through an angle of 42°, find the angle which the emergent ray makes with the second face of the prism. Ans. 18°
5. A ray of light falls normally on a refracting face of a prism (µ =1.5). Find the angle of the prism if the ray just fails to emerge from the prism. Also calculate the angle of deviation. Ans. 42°, 48°
6. A 60° glass prism has refractive index 1.5. Calculate the (i) maximum and (ii) minimum angle of deviation produced by the prism. Ans. 58°, 38°
7. A ray of light is incident at certain angle on a refracting face of a prism of angle 30°. It retraces its path on suffering reflection from the second silvered face of the prism. Calculate the angle of incidence if index of refraction of prism is √2. Ans. 45°
8. Show that a ray of light will not emerge from the prism if A>2C or µ>Cosec(A/2).
9. A prism is made of glass of unknown refractive index. A parallel beam of light is incident on a face of the prism. By rotating the prism angle of deviation is measured to be 40°. What is the refractive index of the prism? If the prism is placed in water (µ=1.33), predict the new minimum angle of deviation of a parallel beam of light. The refracting angle of the prism is 60°. Ans. 1.532, 10° 8´
10. In a spectrometer experiment, the angle of minimum deviation was found to be 48.6°. What is the ٪error in the measurement of refractive index. Given that least count of spectrometer=0.2° and angle of prism=60°. Ans. 0.0554٪
11. An equilateral glass prism (µ=1.6) is immersed in water (µ=1.33). Calculate the angle of deviation produced for a ray of light incident at 40° on one face of the prism. Ans. 14°
12. At what angle should a ray of light be incident on the face of a prism of refracting angle 60°, so that it just suffers internal reflection at the other face. The refractive index of the prism is 1.524. Ans. 29.75°
13. A ray of light passes through an equilateral glass prism such that angle of incidence is equal to angle of emergence. If angle of emergence is ¾ times the angle of prism, calculate the refractive index of glass prism. Ans. √2
14. A thin of angle A and refractive index µ for sodium light is placed at a distance S from a slit illuminated by a sodium light. What is the distance between slit and image formed by the prism? Ans. AS(µ-1)
15. The principal section of glass prism is an isosceles ΔPQR with PQ=PR. The face PR is silvered. A ray is incident perpendicularly on face PQ and after two reflections it emerges from base QR, normal to it. Calculate the angle QPR of prism? Ans. 36°
DUAL NATURE OF MATTER
Q1. What is a photon? Show that it has zero rest mass or photons can not exist at rest. Explain.
Q2. Which photon is more energetic: a red one or violet one. Explain.
Q3. Why are alkali metals most suited as photosensitive metals?
Q4. Why is the wave nature of matter not more apparent to our daily observations?
Q5. The work function of sodium is 2.3eV. Does sodium show photoelectric effect with orange light of wavelength 6800Ǻ?
Q6. A photon and electron have the same wavelength. Which one of them possesses less energy? Explain.
Q7. A photon and electron have got same de-Broglie wavelength(10-10m) which has greater kinetic energy? Explain.
Q8. An electron and proton are possessing same amount of K.E., which of the two have greater de-Broglie wavelength? Justify your answer.
Q9. A proton and an electron have same de-Broglie wavelength. Which of them moves fast and which possesses more K.E. Justify your answer. ____
Q10. Show that de-Broglie wavelength λ of electron of energy E is given by the relation λ=h/√2mE .
Q11. If we go on increasing the wavelength of light incident on a metal surface, what changes in the number of electrons and the energy take place?
Q12. Does each incident photon essentially eject a photoelectron?
Q13. If the frequency of incident light on a metal surface is doubled, will the K.E. of electrons be doubled?
Q14. It is easier to remove an electron from sodium than from copper. Which metal has higher value of threshold frequency?
Q15. Blue light can eject electrons from a photosensitive surface while orange light can not. Will violet and red light eject electrons from the same surface?
Q16. If the intensity of light falling on the emitting substance of a photoelectric cell be increased then what will be the effect on (i) current flowing from the cell, (ii) potential difference required to stop the current completely?
Q17. How is photoelectric effect different from Compton effect?
Q18. Show that the product of the slope of the stopping potential versus frequency graph and the electronic charge gives the value of Planck’s constant.
Q19. Every metal has a definite work function. Why do photo-electrons not come out all with the same energy if incident radiation is monochromatic? Why is there an energy distribution of photoelectrons?
Q20. Show that de-Broglie hypothesis of matter wave supports the Bohr’s concept of stationary orbit.
Q21. Find the de-Broglie wavelength associated with an electron when accelerated under a potential difference of V volts.
Q22. How can de Broglie wave hypothesis be verified experimentally?
Q23. State laws of photoelectric emission. Establish Einstein photo-electric relation. Explain the laws of photo-electric emission on the basis of this relation.
ELECTRIC CHARGES AT REST AND
Q1. How many electrons must be removed from a piece of metal to give it a positive charge of 100nC?
Q2. What is the total charge on 75kg of electrons?
Q3. Calculate the total positive or negative charge on a 3.11g copper penny. Given Atomic mass of copper=63.5, atomic number=29.
Q4. Which is bigger, a coulomb or charge on an electron? How many electronic charges form one coulomb of charge?
Q5. The electrostatic force between charges of 200µC and 500µC placed in free space is 5gf. Find the distance between the two charges. Take g=10m/s².
Q6. How far apart should the two electrons be, if the force each exerts on the other is equal to the weight of the electron?
Q7. Two charges each of +Q units are placed along a line. A third charge q is placed between them. At what position and for what value of q, will the system be in equilibrium?
Q8. Two free point charges +4e and +e are at a distance ‘a’ apart. Where should a third point charge q be placed between them so that the entire system is in equilibrium? What will be the magnitude and sign of q?
Q9.Two small balls having equal positive charge Q on each are suspended by two insulating strings of equal lengths L from a hook fixed in a stand and the whole apparatus is taken in a satellite(state of weightlessness). Find angle between the strings and tension in each string.
Q10. Two electrons have been removed from each of two atoms to make them ions. These ions repel each other with a force of 3.7nN. Find the distance between these ions.
Q11. Two pieces of copper, each of mass 10gm, are 10cm apart. One electron per 1000 atoms is transferred from one piece of copper into the other. How much coulombian force will act between them after the transference of electrons. Atomic weight of copper is 63.5gm/moles.
Q12. Two equally charged identical spheres A and B repel each other with a force of 20µN. Another identical uncharged sphere C is touched to A, then placed at the mid-point between A and B. What is the net electrostatic force on C?
Q13. Two pith balls each weighing 1mg are suspended from the same point by means of silk threads 0.5m long. On charging the pith balls equally, they are found to repel each other to a distance of 0.2m. Calculate the charge on each ball.
Q14. Two identical metallic spheres, having unequal, opposite charges are placed at a distance of 0.90m apart in air. After bringing them in contact with each other, they are again placed at the same distance apart. Now the force of repulsion between them is 0.025N. Calculate the final charge on each sphere.
Q15. Three charges of 5µC, 10µC and -10µC are placed in air at A, B and C corners of an equilateral triangle ABC, having each side 5cm. Find the resultant force on the charge at A.
Q16. Two similar helium filled balloons A and B are fastened to a 5g-wt by threads each 1m long floats in equilibrium. Find the magnitude of the charge on each balloon. Both the balloons carry equal charges(q).
Q17. Consider three charges q1,q2,q3 each equal to q at the three vertices of an equilateral triangle of side l. What is the force on a charge Q placed at the centroid of the triangle?
Q18. A pith ball A of mass 90mg carries a charge of +5µC. What must be the magnitude and sign of the charge on a pith ball B held 2cm directly above the pith ball A such that the pith ball A remains stationary.
Q19. The distance between two equal balls having unlike charges is 2cm. The radii of the balls are much less than the distance between them. The balls attract each other with a force of 0.36mN. After the balls have been connected by a wire and the latter has been removed, the balls repel each other with a force of 0.2025mN. Determine the original charges on the balls.
Q20. A small cork ball with a mass 0.58g is suspended from a thread 10cm long. Another ball is fixed at a distance 10cm from the point of suspension and at a distance of 5cm from the thread. What should the magnitude of the like and equal charges on the balls be to deflect the thread through 30°?
Q21. Point charges having values +0.1µC,+0.2µC,-0.3µC and -0.2µC are placed at the corners A,B,C and D respectively of a square of side one metre. Calculate the magnitude of the force on a charge +1µC placed at the centre of the square.
Q22. A certain charge Q is divided into two parts q and (Q-q). How the charges Q and q be related so that when q and (Q-q) placed at a certain distance apart experience maximum electrostatic repulsion?
Q23. Two small spheres each having mass ‘m’ kg and charge q coulomb are suspended from a point by insulating threads each of lm length, but of negligible mass. If θ is the angle which each string makes with the vertical when equilibrium has been reached, show that q²=4mgl²Sin²θtanθ(4πε۪).
Q24. It is required to hold four equal point charges +q in equilibrium at the corners of a square. Find the point charge that will do this, if placed at the centre of the square.
Q25. A particle of mass m and carrying charge –q1 is moving around a charge +q2 along a circular path of radius r. Prove that period of revolution of the charge –q1 about +q2 is given by T=√(16π³εmr³/q1q2).
Q1. Two small conductors 30cm apart in air are having charges 10nC and 20nC respectively. Find electric intensity at the mid point between them. Ans. 4000N/C along OA
Q2. Two charges each of 200µC, but opposite in sign are 40cm apart. Calculate the electric field at a point 30cm from the mid point on axial line of the dipole.
Q3. Two point charges of +16µC and -9µC are placed 8cm apart in air. Determine the position of the point at which the resultant electric field is zero.
Q4. An oil drop of 12 excess electrons is held stationary under a constant electric field of 25.5kV/m in Millikan oil drop experiment. The density of the oil is 1.26g/cm³. Estimate the radius of the drop.
Q5. A particle of mass m and charge q is thrown at a speed u against a uniform electric field E. How much distance will it travel before coming to momentary rest? Ans. mu²/2qE
Q6. An electron is released from rest in uniform electric field of 1000kN/C. Compute its acceleration. Also find the time taken by the electron in attaining a speed of 0.1c.
Q7. Three charges, each equal to q, are placed at the three corners of a square of side a. Find the electric field at the 4th corner of the square.
Q8. Four point charges of -2qC,+2qC,-qC and +qC are placed respectively at corners A, B, C and D of a square of side 2cm. Find the magnitude and direction of the electric field at the centre O of the square, if q=0.02µC.
Q9. Four charges +q,+q,-q,-q are placed respectively at the four corners of a square of side a. Find the magnitude and direction of the electric field at the centre of the square.
Q10. Four particles, each having a charge q are placed on the four corners A,B,C,D of a regular pentagon ABCDE. The distance of each corner from the centre is a. Find the electric field at the centre of the pentagon.
Q11. A simple pendulum of length L carries a bob of mass m at its lower end. If the bob of the pendulum carries a charge of +qC and is allowed to oscillate in a vertically upward uniform electric field E, find the time period of the pendulum.
Q12. A pendulum bob of mass 80mg and carrying a charge of 20nC is at rest in a horizontal uniform electric field of 20kV/m. Find the tension in the thread of the pendulum and the angle it makes with the vertical.
Q13. A charged particle of mass 1gm is suspended through a silk thread of length 40cm in a horizontal electric field of 40kN/C. If the particle stays at a distance of 24cm from the wall in equilibrium, find the charge on the particle.
Q14. Two point charges of 3µC and -3µC are located 20cm apart in vacuum at points A and B respectively. (a) What is the electric field at the mid point O of the line AB joining the two charges? (b) If a negative test charge of magnitude 1.5nC is placed at the point, what is the force experienced by the test charge?
Q15. A small sphere of mass 1gm carries a charge of +6µC. The sphere is suspended by a string in an electric field of 400N/C acting downward. Calculate the tension in the string. What will be the tension if the charge on the sphere is -6µC.
Q16. Eight identical point charges of qC each are placed at the corners of a cube of each side 0.1m. Calculate electric field at the centre of the cube. Calculate the field at the centre when one of the corner charges is removed.
Q17. A free pith ball of 8gm carries a positive charge of 50nC. What must be the nature and magnitude of charge that should be given to second pith ball fixed 5cm vertically below the former pith ball so that the upper ball is stationary.
Q18. ABC is a right angled triangle, the right angle being at B. Charges of -256,+288 and +81 units are placed at A,B and C respectively. If AB=4cm,BC=3cm, determine the magnitude of electric field at the foot of the perpendicular drawn from B on the side AC.
Q19. Charges of +12nC and -16nC are placed at two points A and B respectively, distance 5cm from each other. Compute the electric field at a point 3cm from A and 4cm from B.
Q20. An electric dipole consists of two charges of 0.1µC separated by a distance of 2cm. The dipole is placed in an external field of 100kN/C. What maximum torque does the field exert on the dipole?
Q21. An electric dipole of length 2cm is placed with its axis making an angle of 30° to a uniform electric field of 100kN/C. If it experiences a torque of 10√3 Nm, calculate (i) magnitude of charge on dipole, and (ii) potential energy of dipole.
Q22. An inclined plane making an angle of 30° with the horizontal is placed in a uniform horizontal electric field of 100V/m from left to right. A particle of mass 1kg and charge 0.01C is allowed to slide down from rest from a height of 1m. If the coefficient of friction is 0.2, find the time it will take the particle to reach the bottom.
Q23. An electron falls through a distance of 1.5cm in a uniform electric field of magnitude 20kN/C. The direction of the field is reversed keeping its magnitude unchanged and a proton falls through the same distance. Compute the time of fall in each case. Contrast the situation with that of ‘free fall under gravity’.
Q1. Electric field at a point due to a point charge is 20N/C and the electric potential is 10J/C. Calculate the distance of the point from the charge and the magnitude of the charge.
Q2. Two charges 4nC and -3nC are located 0.1m apart. At what point on the line joining the two charges is the electric potential zero? Ans. 0.057m from 4nC
Q3. Two charges 30nC and -20nC are located 15cm apart. At what point on the line joining the two charges is the electric potential zero? Ans. 9cm from 30nC
Q4. Eight charged water droplets, each with a radius of 1mm and a charge of 1nC coalesce to form a single drop. Calculate the potential of the bigger drop. Ans. 36kV
Q5. A conducting bubble of radius a, thickness t(t<<a) has potential V. Now the bubble collapses into a droplet. Find the potential of the droplet.
Q6. A thin spherical conducting shell of radius R has a charge q. Another charge Q is placed at the centre of the shell. Find the electrostatic potential at a point P at a distance R/2 from the centre of the shell.
Q7. Three charges 1nC,2nC and 3nC are placed at the corners of an equilateral triangle of side 100cm. Calculate the potential at point O equidistant from three corners of the triangle.
Q8. 2µC is placed at each corner of a square ABCD of side 2√2cm. Calculate electric potential at centre of the square.
Q9. A cube of side b has a charge q at each of its eight vertices. Determine the potential and electric field due to this charge array at the centre of the cube.
Q10. A charge Q is distributed over two concentric hollow spheres of radii r and R(where R>r) such that the surface densities are equal. Find the potential at the common centre.
Q11.Two positive charges of 0.2µC and 0.01µC are placed 10cm apart. Calculate the work done in reducing their distance to 5cm.
Q12. In an atom two protons are separated by a distance of 3Å and an electron is at a distance of 1.5Å from each proton. Calculate the potential energy of this system.
Q13.Point charges of 3nC are located at two vertices of an equilateral triangle of side 20cm. How much work be done to bring a test charge +1nC upto the third corner of the triangle from an infinite distance away?
Q14. ABCD is a square of side 0.2m. Charges of 2nC,4nC,8nC are placed at the corners A,B and C respectively. Calculate the work required to transfer a charge of 2nC from D to the centre of the square.
Q15. Four charges of +q,-q,+q,-q are arranged at the four corners of a square ABCD of side ‘d’. (a) Find the work required to put together this arrangement. (b) A charge q۪ is brought to the centre E of the square, the four charges being held fixed at its corners. How much extra work is needed to do this?
Q16. An electric dipole of length 4cm, when placed with its axis making an angle of 60° with a uniform electric field experiences a torque of 4√3Nm. Calculate the (a) magnitude of the electric field and (b) potential energy of the dipole, if the dipole has charges of ±8nC.
Q17. A charged particle q is shot towards another charged particle Q which is fixed, with a speed v. It approaches Q upto a closest distance r and then returns. If q was given a speed 2v, what would be the closest distance of approach? Ans. r/4 Q18. Three point charges q,2q,8q are to be placed on a 0.09m long straight line. Find the positions, where the charges should be placed such that the potential energy of this system is minimum. In this configuration, what is the electric field at the charge q due to the other two charges?
Q1. An induced current has no direction of its own. Explain, why.
Q2. A rectangular loop and a circular loop are moving out of a uniform magnetic field region to a field free region with a constant velocity. In which loop do you expect the induced e.m.f. to be constant during the passage out of the field region? The field is normal to the loops.
Q3. An aircraft flies along the meridian. Will the potentials of the ends of its wings be the same? Will the potential difference change, if the aircraft flies in any other direction with the same velocity?
Q4. (a) Will the earth’s magnetic field induce current in an artificial satellite with a metal surface that is in orbit around the equator? Around the poles?
(b) If so how would these currents affect the motion of the satellite?
Q5. Why is the coil of a dead beat galvanometer wound on a metal frame?
Q6. A coil A is connected to a voltmeter V and the other coil B to an alternating current source. If a large copper sheet C is placed between the two coils, how does the induced e.m.f. in the coil A change due to current in coil B?
Q7. Self induction is called inertia of electricity. Explain, why.
Q8. What is non-inductive wiring of coils?
Q9. A solenoid with an iron core and a bulb are connected to a
Q10. A copper coil L wound on a soft iron core and a 15W-110V lamp are connected to a 30V battery through a tapping key. When the key is closed, the lamp glows dimly. But when the key is suddenly opened, the lamp flashes for an instant to much greater brightness. Explain, why.
Q11. A small resistor (say, a lamp) is usually put in parallel to the current carrying coil of an electromagnet. What purpose does it serve?
Q12. A magnet is dropped from the ceiling along the axis of a copper loop lying flat on the floor. What differences, if any, will be noticed in the time of fall if (a) the loop is at room temperature, (b) the loop is immersed in ice?
Q13. A magnet is dropped down a long vertical copper tube. What will happen to its ultimate motion?
Q14. A piece of metal and a piece of non-metallic stone are dropped from the same height near the surface of the earth. Which one will reach the ground earlier?
Q15. The divisions marked on the scale of an a.c. ammeter are not equally spaced. Why?
Q16. Prove mathematically that the average value of alternating current over one complete cycle is zero.
Q17. A lamp is connected in series with a capacitor. Predict your observations for
Q18. An applied voltage signal consists of superposition of a
will appear across C and the a.c. signal across L.
Q19. An inductor L of reactance XL is connected in series with a bulb B to an a.c. source. Briefly explain how does the brightness of the bulb change, when (a) number of turns of the inductor is reduced and (b) a capacitor of reactance Xc=XL is included in series in the same circuit.
Q20. Why a.c. is more dangerous than
Q21. At an airport, a person is made to walk through the doorway of a metal detector, for security reasons. If he/she is carrying anything made of metal, the metal detector emits a sound. On what principle does the detector work?
Q22. Can we use 20 c/s a.c. for lightning purposes?
Q23.An electric heater is heated turn by turn by
Q24. Why power factor correction is must in heavy machinery?
HEATING EFFECTS OF CURRENT
Q1. Which bulb has more resistance: (1) 100W; 220V and (2) 60W; 220V Ans. 60W; 220V
Q2. Which electric bulb has greater heat production; a 100W or 200W. Assume that both the lamps are connected to the same supply. Ans. 200W
Q3. The coil of a heater is cut into two equal halves and only one of them is used into heater. What is the ratio of the heat produced by this half coil to that by the original coil? Ans. 2
Q4. Twenty electric bulbs are connected in series with the mains of a 220v supply. After one bulb is fused, the remaining 19 bulbs are again connected in series across the same mains. What will be the effect on illumination?
Q5. What is the material of the element used in an electric heater?
Q6.What is the composition of materials used in the fuse wire?
Q7. State the characteristics of fuse wire.
Q8. Calculate the no. of joules in 1kWh.
Q9. What do you mean by specification of a bulb or other electric appliances?
Q10. If the current in the electric bulb changes by 1% then by what percentage the power will change? Ans. 2%
Q11. Two bulbs, one of 50W and another 25W are connected in series to the mains. Find the ratio of the currents through them. Ans.1:1
Q12. You are given three bulbs of 25, 40 and 60W. Which of them has lowest resistance?Ans.60
Q13. Name the physical quantity which has its unit J/C. Is it a scalar or vector quantity?
Q14.Prove that in parallel combination of electrical appliances, total power consumption is equal to the sum of the powers of the individual appliance.
Q15. A wire connected to a bulb do not glow, whereas the filament of the bulb glows when same current flows through them. Why?
Q16. Explain why an electric bulb becomes dim when an electric heater in parallel circuit is made on. Why dimness decreases after some time?
Q17. Nichrome and copper wires of same length and same diameter are connected one by one between two points of constant potential difference. In which wire the heat will be produced at higher rate? Explain.
Q18. Nichrome and copper wires of same length and same diameter are connected in series in the electric circuit. In which wire, the heat will be produced at higher rate? Explain.
Q19. There is a frill of 20 bulbs (connected in series) in a room. One bulb is fused. The remaining 19 bulbs are again joined in series and connected to the same supply. Will the light increase or decrease in the room?
Q20. Water boils in an electric kettle in 15 minutes after being switched on. Using the same main supply, should the length of the heating element be increased or decreased if the water is to boil in 10 minutes? Explain.
Q21.How does the use of fuse wire save the electrical installations?
Q22.A toaster produces more heat than a light bulb when they are connected in parallel. Which has the greater resistance?
Q23. By what percentage will the illumination of the lamp decrease if the current drops by 20%?
Q24. Prove that in series combination of electrical appliances the reciprocal of total power consumption is equal to the sum of the reciprocal of the powers of the individual appliances.
1. In Young’s double slit experiment, while using a source of light of wavelength 5000Å, the fringe width obtained is 0.6cm. If the distance between the screen and slit is reduced to half, what should be the wavelength of the source to get fringes 0.003m wide?
2. A double slit is illuminated by light of wavelength 6000Å. The slits are 0.1cm apart and the screen is placed 1m away. Calculate (i) angular position of 10th maximum in radian (ii) separation of two adjacent minima.
3. The two slits in Young’s double slit experiment are separated by distance of 0.03mm. When light of wavelength 5000Å falls on the slits, an interference pattern is produced on the screen 1.5m away. Find the distance of 4th bright fringe from the central maximum.
4. In Young’s double slit experiment, the slits are 0.2mm apart and the screen is 1.5m away. It is observed that the distance between the central bright and 4th dark fringe is 1.8cm. Calculate wavelength of light used. Ans. 686nm
5. In Young’s experiment, the width of the fringes observed with the light of wavelength 6000Å is 2mm. What will be the fringe width of the entire apparatus immersed in a liquid of µ=4/3. Ans. 1.5mm
6. The widths of two slits in Young’s experiment are in the ratio 9:4. Calculate the intensity ratio in the interference pattern. Ans. 25:1
7. The intensity ratio in the interference pattern is 1:9. What is the amplitude ratio and the ratio of width of two slits? Ans. 2:1, 4:1
8. What change is observed in interference pattern of Young’s double slit experiment, if one of the two slits is painted, so that it transmits half the light intensity of the other?
9. In a Young’s double slit experiment, red light of wavelength 6000Å is used and the nth bright fringe is obtained at a point P on the screen. Keeping the same setting, the source is replaced by green light of 5000Å and now (n+1)th bright fringe is obtained at the point P. Calculate the value of n. Ans. 5
10. In Young’s double slit experiment, light of wavelength 6000Å is used to get an interference pattern on a screen. The fringe width changes by 1.5mm, when the screen is brought towards the double slit by 50cm. Find the distance between the two slits.
11. Two coherent sources of intensity ratio β interfere. Prove that in interference pattern, (Imax-Imin)/(Imax+Imin)=2√β/(1+β)
12. A beam of light consisting of two wavelengths 4800Å and 6000Å is used to obtain interference fringes in a double slit experiment. The distance between the slits is 1.8mm and the distance of screen from the plane of slits is 1.2m. (a) Find the distance of the 5th bright fringe from the centre of the screen for the wavelength 6000Å. (b) What is the least distance from the centre of the screen, where the bright fringes due to both the wavelengths coincide? Ans. (a) 2mm (b) 1.6mm
13. Find the maximum intensity in case of interference of n identical sources each of intensity I if the interference is (i) coherent (ii) incoherent. Ans. n²I, nI
14. White light is used in Young’s double slit experiment. The separation between the slits is b and screen is placed at large distance D(D>>b). At a point directly in front of one of the slits, certain wavelengths are missing. Find the missing wavelengths.
15. In double slit experiment, SS2 is greater than SS1 by 0.25λ. Calculate the path difference between the two interfering beams from S1 and S2 for minima and maxima on the screen. Given distance between slits is d and distance of point P from the centre is x.
16. In Young’s double slit experiment, we observe the 10th maximum for λ=7000Å. What order will be visible if the source of light is replaced by light of wavelength 5000Å?
17. In Young’s double slit experiment, two slits are separated by 5mm. A light of wavelength λ=5500Å falls on the slits. The distance of the screen is 2m from the plane of the slits. Calculate the separation between 10th bright fringe and 3rd dark fringe, with respect to central maximum. Ans. 1.65mm
18. In Young’s double slit experiment, using light of wavelength 400nm, interference fringes of width ‘X’ are obtained. The wavelength of light is increased to 600nm and the separation between the slits is halved. If one wants the observed fringe width on the screen to be the same in the two cases, find the ratio of the distance between the screen and the plane of the interfering sources in the two arrangements. Ans. 3:1
MAGNETIC EFFECTS OF CURRENT
Q1. Of the three vectors in the equation F=q(vxB), which pairs are always at right angles? Which may have any angle between them?
Q2. A beam of protons is deflected sideways. Could this deflection be caused (a) by an electric field? (b) by a magnetic field? (c) If either is possible, how can you tell which one is present?
Q3. In what respect does a wire carrying current differ from a wire which carries no current?
Q4. What do you understand by the term current element? What is its S.I. unit? What is the significance of current element?
Q5. Write an expression for the Lorentz force acting on a charged particle.
Q6. Is the source of magnetic field analogous to the source of electric field?
Q7. What type of fields are produced by moving proton? By stationary proton?
Q8. A beam of protons are moving vertically upwards enters a magnetic field directed towards south. What is the direction of the force on the charge?
Q9. If an electron is not deflected in passing through a certain space, can we be sure that there is no magnetic field in that region?
Q10. A static magnetic field cannot change the kinetic energy of a moving charged particle. It can deflect the charged particle sideways. Comment.
Q11. Free electrons always keep on moving in a conductor. Even then, no magnetic force acts on them in a magnetic field unless a current is passed through it. Why?
Q12. A charged particle is released from rest in a region of steady and uniform electric and magnetic fields, which are parallel to each other? What will be the nature of the path followed by a charged particle?
Q13. A charged particle is projected with velocity v in a uniform magnetic field at an angle Ө(0< Ө <90°). What will be the path of the charged particle? Justify your answer.
Q14. Both the electric and magnetic fields can deflect a moving electron. What is the difference between these deflections?
Q15. Why should a solenoid tend to contract when a current passes through it?
Q16. What is the main function of a soft iron core used in a moving coil galvanometer?
Q17. Why is ammeter connected in series and voltmeter in parallel in the circuit?
Q18. By mistake a voltmeter is connected in series and an ammeter is connected in parallel, with a resistance in an electrical circuit. What will happen to the instruments?
Q19. Why do magnetic lines of force prefer to pass through iron than air?
Q20. Why electromagnets are made of soft iron?
Q21. What happens if a bar magnet is cut into two pieces (i) transverse to its length (ii) along its length?
Q22. What happens if an iron bar magnet is melted? Does it retain its magnetism?
Q23. A certain region of space is to be shielded from magnetic fields. Suggest a method?
Q24. State and explain Curie’s law in magnetism?
Q25. What is meant by hysteresis? Discuss briefly the dissipation of energy due to hysteresis.
Q26. What is Ampere’s circuital law? Derive an expression for magnetic field induction due to current in a solenoid?
Q27. Derive an expression for force on a current carrying conductor placed in magnetic field?
Q28. Derive an expression for torque acting on a current carrying coil suspended in a magnetic field?
Q29. Discuss with the help of a neat diagram the construction and theory of a moving coil galvanometer.
Q30. How can a galvanometer be converted into (i) an ammeter and (ii) voltmeter?
Q31. What is cyclotron? Discuss its construction, working and theory. Explain cyclotron frequency.
Q1. Define refractive index of the material? (1)
Q2. How does the focal length of a convex lens change if monochromatic red light is used instead of monochromatic blue light? (1)
Q3. What happens to the power of a lens immersed in water? (1) Q4. Can a convex lens behave like a concave lens? Explain. (1)
Q5. To a fish under water viewing obliquely a fisherman standing on the bank of a lake, does the man look taller or shorter than what he actually is? (1)
Q6. A concave mirror is placed in water. Will there be any change in focal length?
Give reasons? (1)
Q7. What type of lens an air bubble behave inside water? (1)
Q8. Does critical angle depend on colour of light? (1)
Q9. The image of a candle is formed by a convex lens on a screen. If the lower half of the lens is covered with black paper so that it is perfectly opaque. Will the full size of the image be obtained? (1)
Q10. An equiconvex lens of radius of curvature R is cut into two equal parts by a vertical plane. What will be the focal length of each part? (1)
Q11. Why the power of a lens is measured as the reciprocal of its focal length? (1)
Q12. The image of an object formed by a lens on the screen is not in sharp focus. Suggest a method to get clear focusing of the image on the screen without disturbing the position of the object, the lens or the screen. (1)
Q13. Vehicles moving in foggy weather use yellow colour headlights. Why? (1)
Q14. An object is first seen in red light and then in violet light through a simple microscope. In which case is the magnifying power larger? (1)
Q15. Only the stars near the horizon twinkle while those overhead do not. Why? (2)
Q16. The refractive index of the material of a concave lens is n. It is immersed in a medium of refractive index n1. A parallel beam of light is incident on the lens. Trace the path of emergent rays in each of the following cases: (i) n1>n (ii) n1<n (iii) n1=n (2) Q17. A beam of light is converging towards a point on a screen. A plane parallel plate of glass is introduced in the path of this converging beam. How will the point of convergence be shifted? Draw the ray diagram. (2)
Q18. Why does sky look blue? (2)
Q19. Why sun appears reddish at sunset and sunrise? (2)
Q20. What is total internal reflection? Under what conditions does it take place? (2)
Q21. Prove Brewster’s law? (2)
Q22. When a ray of light incident on a glass slab what is the lateral shift of the ray of light? (3)
Q23. Derive lens formula for a concave lens? (3)
Q24. Discuss refraction at convex spherical surface when object lies in rarer medium and image formed is real. Also write the assumptions and sign conventions used. (5)
SOLIDS AND SEMICONDUCTOR DEVICES
Q1. Why is it difficult to make intrinsic semiconductors? (1)
Q2. How does the conductivity of a pure semiconductor change with rise in temperature? (1)
Q3. Will Ohm’s law be obeyed or not in a semiconductor? Explain. (1)
Q4. What is Fermi level? (1)
Q5. What is a crystal lattice? (1)
Q6. Define forbidden energy gap in solids? (1)
Q7. Where are donor and acceptor levels located in a semiconductor? (1)
Q8.What is doping? What are necessary conditions for it? State two methods of doping. (2)
Q9. Why does a semiconductor get damaged when strong current flows through it? (2)
Q10. What is the charge on N-type semiconductor ? Explain. (2)
Q11. Distinguish between conductors, semiconductors and insulators on the basis of their energy bands. (3)
Q12. Explain formation of energy bands in solids and hence define conduction band and valence band. (3)
Q13. What is an ideal p-n junction diode? (1)
Q14. Can we take one slab of P-type semiconductor and physically join it to another N-type semiconductor to get P-N junction? (1)
Q15. Can two separate p-n junction diodes placed back to back be used to form a p-n-p transistor? (1)
Q16. What is Zener breakdown? (1)
Q17. Would you prefer to use a transistor as a common base or a common emitter amplifier? (1)
Q18. Why is a transistor so called? (2)
Q19. When a P-N junction diode is formed, what stops all the electrons to flow from N-region to P-region, although N-type semiconductor has excess of free electrons? (2)
Q20. In a transistor, base is made thin and doped with little impurity atoms. Why? (2)
Q21. Explain the formation of (i) potential barrier and (ii) depletion region in a p-n junction diode. (3)
Q22. Explain the use of P-N junction diode as a full wave rectifier. (3)
Q23. Describe an experimental set up for drawing the common emitter characteristics of a PNP transistor. Discuss their shapes (5)
Q24. Explain the working and amplifying action of a transistor. Also define current gain, voltage gain and power gain. (5)
Q25.How a P-N-P transistor acts as an oscillator? Explain. (5)
Q26. What is a digital signal? (1)
Q27. What is an analog signal? (1)
Q28. What is a logic gate? (1)
Q29. What is a digital circuit? (1)
Q30. Why are the NAND (or NOR) gates called as a digital building block? (1)
Q31. Give logic symbol, Boolean expression and truth table of an AND gate. (2)
Q32. Give the logic symbol, truth table and Boolean expression for a NOT gate. (2)
Q33. Give the logic symbol, Boolean expression and truth table of NAND logic gate. (2)
Q34. Give the advantages and limitations of integrated circuits over conventional electronic circuits.
Q1. What evidence is there to show that sound is not electromagnetic in nature? (1)
Q2. Sketch the refracted wavefront emerging from a convex lens if a plane wavefront is incident normally on it. (1)
Q3. How does the intensity of central maximum change, if the width of the slit is halved in a single slit diffraction experiment? (1)
Q4. Is sunlight polarized? (1)
Q5. Is the blue light from sky polarized or not? (1)
Q6. Can we observe interference maxima on the screen if the two slits are separated by less than a wavelength of light used? (1)
Q7. One of the two slits in young’s double slit experiment is so painted that it transmits half the intensity of the other. What is the effect on interference fringes? (1)
Q8. What is the effect on interference fringes in young’s double slit experiment if one slit is covered? (1)
Q9. Two slits in young’s double slit experiment are illuminated by two different sodium lamps emitting light of same wavelength. Do you observe any interference pattern on the screen? (1)
Q10. A single slit diffraction pattern is completely immersed in water without changing any other parameter. How is the width of central maximum affected? (1)
Q11. How does diffraction limit the resolving power of an optical instrument? (1)
Q12. Why are longitudinal waves not polarized? (1)
Q13. Why is diffraction of sound waves easier to observe than diffraction of light waves?
Q14. Stars are often photographed using blue filter. Why? (2)
Q15. Two polaroids are placed at right angle to each other. What will happen to the intensity of transmitted light when one more Polaroid is placed between these two bisecting the angle between them? (2)
Q16. For slit of width ‘a’ estimate the distance upto which ray optics is valid? (2)
Q17. Two polaroids are crossed to each other. When one of them is rotated through 60°, then what percentage of the incident unpolarised light will be transmitted by the polaroids? (2)
Q18. Two slits are made 1mm apart and the screen is placed 1m away and light of wavelength 500nm is used. What should be the width if each slit to obtain 10 maxima of the double slit pattern within the central maximum of the single slit pattern? (2)
Q19. Discuss laws of refraction on the basis of Huygen’s principle? (3)
Q20. State Huygen’s principle? (3)
Q21. What are conditions for Sustained interference? (3)
Q22. What is the difference between interference and diffraction? (3)
Q23. State and prove law of malus? Also discuss special cases? (3)
Q24. Define angular dispersion and dispersive power? (4)
Q25. Discuss diffraction of light at a single slit. Obtain conditions for maxima and minima. Also obtain the expression for width of central maximum? (4)
Q26. Discuss Basic theory of interference. Find conditions for constructive and destructive interference? Also find the positions of maxima and minima? (5)