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Competency Based Questions, GMultiple Choice Questions 1Mark, 1. A conducting rod of length l is kept parallel, , to a uniform magnetic field B. It is moved, alongthemagneticfield with a velocity 7.What, is the value of emf induced in the conductor?, (A) Zero, , (B) One, , (C) Two, , (D) Three, , Explanation: Emfis induced when there is, , change in the rate of the flux but here velocity, , it constant and magnetic field is uniform, so, no change in flux takes place and the induced, emf is zero., , (C) 6 Henry, , (D) 8 Henry, , Ans. (A) 2 Henry, , Write all the, , things given, , Ans. (B) Copper, , (A) 99 V, , (B) 100 VN, , (C) 102 V, , (D) 105 V, , (C) 5 times, , (D) 6 times, , Ans. (B), , 4, , starting., , Explanation, EME, , E -Bol, , Given: B = 0.5 T, o, , 3. The number of turns of a solenoid are, doubled without changing its length and, area of cross-section. The self-inductance of, (B) 4 times, , in the, , Ans. (B) 100 V, , copper., , (A) 3 times, , question, , normal to the rod passing through its one, end. The other end of the rod is in contact, with a circular metallic ring. A constant and, uniform magnetic field of 0.5 T parallel to, the axis exists everywhere., Calculate the emf developed between the, centre and the ring., , (D) None of these, , the solenoid will become . . ., , in the, , angular velocity of 400 rad/s about an axis, , B) Copper, , the loops will be same, as it depends only, upon the magnetic field and angular velocity., But resistivity of aluminium is greater than, copper. So, induced current will be more in, , = 2 H], , 5. A 1.0 m metallic rod is rotated with an, , field. In which of the two coils will the, induced current be more ?, , Explanation: The induced emf in both, , 2x 102, 102, , (A Enhance your Answer, , 2. Two identical coils, one of copper and the, other of aluminium are rotated with the, same angular speed in an external, magnetic, , (A) Aluminium, (C)Both (A) and (B), , (B) 4 Henry, , Explanation:, L, L= =2x102, 0.01, , Ans. (A) Zero, , a, , (A) 2 Henry, , E, , = 400 rad/s, l = 1 m, , x0.5 x400 x(1), = 0.5 x 200, , times., , 100 V, , 6. A pair of adjacent coils has a mutual, inductance of 1.5 H. If the current in one coil, changes from 0 to 20 A in 0.5 s, what is the, change of magnetic flux linkage with the, , times, , other coils?, , Explanation : As self inductance of a long, , (A) 20 Wb, , solenoid,, L, , =, , (B) 25 Wb, , HoNA, , (C) 30 Wb, , (D) 35 Wb, , i.e., 4., , LN2, , The magnetic flux linked with a coil changes, by 2 x 10-2 wb when the current changes, by 0.01 A. The self-inductance of the coil is, ************., , Ans., , (C) 30 Wb, , Explanation: Magnetic flux, 2 = MI, Change in magnetic flux, A¢2 = MAl, , It is given: M = 1.5 H, Al, , = 20-0, , Ad2 = 1.5 x 20, , 20 A, , 3 0 Wb.

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7. There are two coils A and B separated, by some distance. If a current of 2A flows, , through A, a magnetic flux of 10-2 wb passes, through B (no current through B). If no, current passes through A and a current of 1 A, , passes through B, what is the flux through, A., , towards B, current induced in B is counto., , clockwise direction as per Lenz's law. Th, current in B would, , stop when A, , moving, , 9. The magnetic susceptibility of magnesium, , at 300 K is 1.2 x 10. The temperature when, its, , magnetic, , susceptibility will become, , (A) 3 m Wb, , (B) 4 m Wb, , 1.44x 10 is:, , (C) 5m wb, , (D) 6 m Wwb, , (A) 250 K, , (B) 275 K, , (C) 175 K, , (D), , Ans. (C) 5 m Wb, , Explanation : Mutual inductance ofcoil B, due to coilA,, , Explanation:, , 1, , T, T2, , 2, Ma1 1, =0--=, = 5 mH, , m2, , 2, , 1.2x 10, 1.44 x 10, , M2 = 9, , Also,, , N01, , =, , x 300 = 250 K, , 10. The self-inductance L of a solenoid of length, , 2, , or, , None of these, , Ans. (A) 250 K, , N,02, , Ma, , ops, , M12l2=, , 5, , x, , I and area of cross-section A, with a fixed, , 11, , number of turns N increases as:, , = 5 m WNb., , (A) bothl and A increases, , (B) there is a varying current in A, (C) there is no current in A, (D) there is a constant current in the, , Mistakes to Avoid, Here, M21, , IS, , mutual inductance of coil B due to coil A., , counter, , clockwise direction in A, , (AEnhance your Answer, , Ans. (B) there is a varying current in A, , Write the correct units involved., shown in, starts, current, flowing in B as, figure. A, shown, when A is moves towards B and, , 8. There, , stops, , are, , two coils A, , when A, , and B, , stops moving., , as, , The, , current, , in, , A is counter clockwise. B is kept stationary, when A moves. We can infer that:, , As emf is induced when the, , flux linked with the coil changes., 11. The direction of induced emf can be found, , by, (A) Kirchhoff's voltage law, (B) Kirchhoff's current law, (C) Lenz's law, , B, , A, , Explanation:, , D) Fleming's Right hand rule, Ans. (C) Lenz's law, , Explanation: Lenzs law named afterthe, is a constant, clockwise direction in A, , (A) there, , (B) there, (C) there, , (D), , a, , is, , no, , a constant current, , direction., , Because, , in, of, , counter, , in the counter, , counter, , that,, , Emil Lenz who formulated it in, , states, , that the direction of the electrnc, the, , changing magnetic field is such that, magnetic field created by the induced current, opposes changes in the initial magnetic ield, , a, , Coil A must be carrying, , current, , physicist, , current which is induced in a conductor by, , current in A, , there is, clockwise direction in A., , constant, , the, , varying current in A, , is, , Explanation, a, , in, , 1834,, , there is a constant current in the, clockwise direction in A, , (D), Ans., , current, , clockwise, , when, , moves, , 12. Which of the, , following, , is the unit, , inductance ?, , (A) ohm, , (B) Henry, , (C) Ampere-turns, , (D) Weber/metre, , Ans. (B) Henry, , o

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Explanation, , of either, , self, inductance or mutual inductance abbreviated, H and named for the American physicist, Joseph Henry. One Henry is the value of self:, , Henry,, , unit, , inductance in a closed circuit or coil in which, , one volt is produced by a variation of the, inducing current of one ampere per second., , of conservation of energy?, (B) Faraday's law, (A) Lenz's law, , (D), , (C)Ampere's law, , Biot Savart law, , Ans. (A) Lenz's law, 19. The induced emf cannot be produced by, (A) moving a magnet near a circuit, (B) moving a circuit near a magnet, , Scan Yourself*, of the following scientists is, not connected with the electromagnetic, , 13. Which, , 18. Which of the following is based on the law, , one, , induction?, , (A) Faraday, , (B) Lenz, , (C) Henry, , (D) Ohm, , (C) changing the, , in, , current, , placed near the other, (D) maintaining large but, , one, , circuit, , constant current, , in a circuit, Ans. (D) maintaining large but constant current in, a circuit, , Ans. (D) Ohm, , 20. Two coils are placed close to each other, as shown in the figure. When the key K is, , 14. The unit of magnetic flux in SI is:, (A) Weber, , (B) Gauss, , pressed a current flows in the secondary, , (C) Oersted, , (D) Tesla, , coil ABCD. What happens on breaking the, circuit?, , Ans. (A) Weber, , 15. The magnetic flux through a coil is inverselyy, , proportional to:, (A) number of turns (B), (C) magnetic field (D), , area, none, , of these, , Ans. (D) none of these, , 16. The, a, , expression, , K, , for the, , negative sign| E, , induced, , do, , "., =-dt, , emf contains, , What is the, , significance of the negative sign ?, (A) The induced emf is produced only when, the magnetic flux decreases, , (B) The induced emf opposes the changes in, the magnetic flux, , (C), , The induced emf is, direction of the flux, , opposite, , to, , (B), , No current flows in the coil s, A current, , greater in magrnitude but same, , in direction flows through the coil, (C) The magnitude of the current is greater, , but direction is reversed, , (D), , The, , magnitude, , of the current is lower, , and direction is reversed, , Ans. (C) The magnitude of the current is greater, , but direction is reversed, , The induced emf opposes the, , changes in, , the magnetic flux, 17. Which of the following phenomena makes, , 21. Dynamo is designed on the principle of, (A) Electromagnetic induction, (B) Self induction, , use of electromagnetic induction ?, , (C) Mutual induction, , (A) Charging a storage battery, , (D), , (B) Magnetising an iron piece with a bar, , (C)Generation of hydroelectricity, () Magnetising a soft iron piece by placing, inside a current carrying solenoid, , (C) Generation, , None of these, , Ans. (A) Electromagnetic induction, 22. What does a dynamo generate ?, , magnet, , An's., , (A), (B), , the, , (D) none of these, , Ans., , C, , of, , hydroelectricity, , (A) Electrons, , (B) Charge, , (C) emf, , (D) None of these, , Ans. (C) emf

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23. What is motional emí ? It is, the induced, emf:, , (A) across the ends of a wire moving in a, magnetic field, (B) in a coil due to the motion of the, near it, , magnet, , (C) in a circuit due to variation in its own, current, , in the neighbouring circuit, , (A), , Less than, , (B), (C), , One ampere per second, Two ampere per second, More than two ampere per second, , (D), Ans. (B), , one, , One ampere per second, , 30. Which of the following is NOT a factor t, determine the mutual inductance of the twa, coils?, , (D) in a circuit due to the variation of current, Ans., , ampere per second, , (A), , the ends of a wire moving in a, magnetic field, 24. The force between two current, carrying8, across, , parallel wires is due to:, (A) Electrostatic interaction, , Ans. (C) Current through each coil, 31. Which of the following is NOT he function, , oftransformer?, , (B) Magnetic effect of electric current, (C) Electric effect of magnetic field, , (D) Electromagnetic induction, Ans. (B) Magnetic effect of electric current, 25. The frequency (in Hz) of the commercial, , alternating current generated in India is, (A) 50, (C) 110, , (A) The number of turns of each coil, (B) The shape of each coil, (C) Current through each coil, (D) Separation between the coils, , (A) Transform magnetic energy into electric, energy, (B) Transfer electrical energy from one part, of the circuit to another, , (C) Step up or step down the voltage, (D) Decrease or increase, , (B) 60, , Ans. (A) Transform magnetic energy into electric, , Ans. (A) 50, , 26. Which of the following is used to determine, the direction of induced current in a, generator?, , energy, 32. Which of the following instruments do not, make use of eddy currents?, , (B) Fleming's right hand rule, , (A) Electrical brakes, (B) Induction motor, , (C) Maxwell's cork screw rule, , (C) Transformer, , (D) Ampere's swimming rule, , (D) Dead beat galvanometer, , (A) Fleming's left hand rule, , Ans. (B) Fleming's right hand rule, 27. The current from which of the, following, devices does not vary in magnitude?, (A) Transformers, (B), , Dynamo, , D) Induction coil, , Ans. (C) Cell, 28. Which of the, , Henry?, , following, , (A) volt-second, ampere, C, , Volt", , -, , second, , coulomb, , is not, , equal, , to, , Ans. (C) Transformer, 33. The transformer is devised, , coulomb, , (A) self induction (B), (C) eddy currents (D), Ans. (B) mutual induction, , 35. The, , Coulomb, , none, , 29. What should be the, rate of current in, circuit of self inductance 1, , coupling coefficient, , (B) 1, a, , Henry to generate, , induced emf equal to one volt ?, , none, , of these, , galvanomete, , of these, , (A) zero, , coulomb, , principle, , (B) Mutual induction, (D) none of these, , coupled coils is:, , Ans. (C) volt"-second, , the, , mutual induction, , 34. The coil of the, ballistic, , Ans. (D), , (D) Oule-second2, , on, , of, , oscillates due to:, (A) Self induction, (C) Eddy currents, , volt - second, , (B), , alternating, , current, , (D) 220, , (C) Cell, , the, , (C) slightly more than 1, (D) infinite, Ans. (B) 1, , of the, , perfecut

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36. The motional emf produced across a wire, moving through a magnetic field does not, , C), , 1, , velocity of the rod, , depend on its:, , (B) Length, , (A) Velocity, , (D) Orientation, , (C) Diameter, Ans., , (D), , (C) Diameter, , 37. Which of the, , following, , is, , independent, , of, , the direction ofthe current in a circuit?, , (A) Mutual induction, , 1, , magnitude, , of the, , magnetic field, , Ans. (B) rate of change of magnetic flux, 42. What determines the charge that flows, through a circuit due to the induced emf?, (A) The rate of change of magnetic flux, , (B) Joule's heating, , (B) The total change in magnetic tlux, , (C) Electrolysis, , C) The initial magnetic flux, , (D) None of these, , (D) The final magnetic flux, , Ans. (B) Joule's heating, 38. The north pole of a bar magnet is rapidly, introduced into a solenoid at the end A., Which of the following statements correctly, depicts the phenomenon taking place ?, (A) No induced emf is developed, (B) The end A of the solenoid behaves like a, south pole, , (C) The end A of the solenoid behaves like a, north pole, (D) The end A of the solenoid acquires, , positive potential, Ans. (C) The end A of the solenoid behaves like a, north pole, , 39. In which of the following cases with a bar, magnet and the solenoid, no induced emf is, , Ans. (B) The total change in magnetic flux, , 43. The magnetic flux () linked with a coil due, to its own magnetic field is related to the, , number of turns () of the coil as:, (B) o oc nz, (A) o cn2, , (C) a n, Ans. (A) ¢«n, , 44. The magnetic flux ()) linked with a coil is, , related to the area (A) of the coil as:, , (A) o oc A-1/2, , C) orA, , that can be obtained with the help of three, , inductances of 2 H, 3 H and 6 H?, , (A)H, , (A) When magnet is inserted, , C) 1H, , (C) When coil is moved towards or away, from the magnet, (D) When the relative velocity of the coil w.rt, the magnet is zero, Ans. (D) When the relative velocity of the coil w.rt, , the magnet is zero., 4. A copper rod moves parallel to the horizontal, , direction. The induced emf developed, across its ends due to earth's magnetic field, , will be maximum at the:, A) equator, (B) latitude 30°, (C) latitude 60°, (D) poles, Ans. (D) poles, , . Acopper rod is moved in a magnetic field., The charge, developed across its ends will be, proportional to :, (A) magnetic flux, , (B) rate of change of magnetic flux, , (B) oc A12, (D) A-1, , Ans. (C) acA, 45. What is the minimum value of inductance, , produced?, (B) When magnet is withdrawn, , (D) cn, , (D) 11 H, , ns. (C) 1H, 46. No current is drawn from the secondary coil, of an ideal transformer. What is the power, factor of the primary coil?, (A) 1/2, (B) 1, , (C), , (D) Zero, , Ans. (D) Zero, 47. In the circuit shown, , below, what, , the reading of the ammeter, closing the key ?, 52, w".., , 10V, , long, , 52, , www, , 52, , (A) 1A, , (B) 2A, , (C) (4/3) AA, , (D) (3/4) A, , Ans. (C) (4/3) A, , will be, time after, , 10 H

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48. A long straight wire lies along the axis of, long straight solenoid. The wire carries a, current I = Io sin ot. The induced emf may, , be expressed as:, (A) E = Eo sin ot, (B) E = Eo cos ot, , (C) good conductor, (D) bad conductor, , Ans. (C) good conductor, 56. What happens when a magnet is dropped, two ends are, into a solenoid, whose, connected to each other. While crossing the, , loop, it will fall, , (C) E = constant, , with acceleration., , (A) equal to g, , (D) E = zero, , Ans. (D) E= zero, 49. The Lenz's law is the consequence to the, , (B) less thang, (C) more than g, less than g above the coil and, g below it, , (D), , conservation of, , (A) charge, , (B) momentum, , (C) ener8y, , (D) none of these, , 50. The induced emf in a coil is independent of, (A) resistance of the coil, , than, , Ans. (B) less than g, , 57. The, , And. (C) energy, , more, , current in, , the armature of dc motor is, , the maximum, when the motor is, (A) switched off, (B) switched on, , (B) number of turns, , (C) running at full speed, (D) running at intermediate speed, , (C) rate of change of flux, D) none of these, , Ans. (B) switched on, , Ans. (A) resistance of the coil, 51. If the magnetic flux linked with a coil, through which a current of xA is set up, is, self-inductance, y Wb, then the coefficient of, ofthe coil is:, , (A) (x- y) Henry, , 58. A, , coil, , is, , rectangular, , wound, , X, , of, , dimensions of the transformer are increased, a factor 2 and the number of turns per unit, , by, , length of, , unchanged,, , the coil remains, , the, , self inductance of the coil will be increased, , B)Henry, , by a factor:, 8, , (A) 16, , C)Henry, , transfomer, , a, , on, , cross-section. If all the linear, , (D) xy Henry., , (D) 2, , (C) 4, , Ans. (B) 8, 59. The induced emf LdlVdt is analogous in, , Ans. (C) Henry, , mechanics to, , 52. When the number of turns of, , a, , coil is, , doubled, its self inductance, (A) is doubled, , (B) is halved, , (C) becomes one quarter, , (D), , becomes four times, , Ans. (D) becomes four times, , 53. Eddy currents do not cause, , (A) damping, , (B) heating, , (C) sparking, , D) loss of energy, , Ans. (C) sparking, 54. The role of inductance is equivalent to:, , (A) force, , (B) work, , (C) power, , (D) impulse, , Ans. (A) force, , 60. Which of the following in electrodynamics is, , to the momentum in mechanical, dynamics ?, , analogous, (A) VI, , (B) qV, , (C) LI, , (D) Ldl/dt, , Ans. (C) LI, , 61. A straight line conductor of length 0.4 m is, moved with a speed of 7 m/s perpendicular, , (A) momentum, , B) force, , to a magnetic field of intensity 0.9 Wb/m, , (C) energy, , D) inertia, , The induced e.m.f., , Ans. (D) inertia, 55. In the dead beat galvanometer, the coil is, wound on a frame made of :, , (A) magnetic material, B) non-magnetic material, , across, , the conductor is, , (A) 5.04 V, , (B) 1.26 VV, , (C) 2.52 V, , (D) 25.2 V, , Ans. (C) 2.52 V, , 62. The induced emf of 2V is generated when, the, , current, , in the circuit, , changes, , from 4A

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Ans., , to 5A in one millisecond. What is the self, , (A) 3 volt, , (B) 7.5 volt, , inductance of the circuit ?, , (C) 15 volt, , (D) 30 volt., , (A) 8H, , (B) 10 H, , (C) 80 H, , (D) None of these, , (D), , Ans. (A) 3 volt, 70. The equation of A.C. is represented by, , None of these, , e = eo sin ot. In what time the e.m.f. will, be half of its maximum value starting from, , 63. The magnetic flux linked with a coil varies, with time as : = 3t + 4t +9 Weber. What is, , zero?, , the induced emf att= 2s?, (A) 3V, , (B) 4V, , (C) 9V, , (D) 16 V, , (A), Ans. (C), , Ans. (D) 16 V, , 64. What voltage is developed across the axle, of the wheels of a train, when it moves, , with a speed of 72 kmh, , T, , (B), , (C), , T, , 12, , (B) Weber + Volt, , 0.40 x 10T and the angle of dip is 30°. The, , (C) Weber - Ampere, , length of the axle is 1.5 m., , D) Weber - Volt, , (C)0.6mV, , Ans., , Ans. (C) 0.6 mV, , 65. What is the energy stored in a 50 mHI, inductor carrying a current of 4A ?, , (A) 0.4J, , (C)0.1J, , (D), , (A) Weber + Ampere, , ? The horizontal, , (B) 0.4 mV, (D) 0.8 mVv, , 2, , 71. 1 Henry =, , component of the earth's magnetic field is, , (A) 0.2 mV, , T, , (A) Weber + Ampere, , 72. The induced emf in a coil rotating in a, magnetic field is maximum when the, angle between the plane of the coil and the, , direction of field is, (A) zero, , (B) 0.2J, D) 0.05J, , B), , Ans. (A) 0.4J, 66. A transformer is used to light a 100W and, 110 V lamp from a 220 V mains. If the, main current is 0.5 A. The efficiency of the, , transformeris:, (A) 11%, , (B) 50%, , (C) 80%, , (D) 90%, , Ans. (D) 90%, 67., , When the current changes from + 2A to -, , 2A, , in 0.05 second, an e.m.f. of 8 volt is induced, in a coil. The coefficient of self induction of, , thecoil is:, (A) 0.1 H, , (B) 0.2H, , C)04H, , (D) 0.8H, , Ans. (A) 0.1 H, 68. Two coils X and Yare placed in a circuit such, , that a current changes by 3 Ampere in coil X, and the magnetic flux changes of 1.2 weber, OCCurs in Y. The value of mutual inductance, , of the coils is, (A) 0.2 Henry, (C) 0.6 Henry, , Ans. (B), , 0.4, , (B) 0.4 Henry, , (C), (D) some angle other that those mentioned, above, , Ans. (A) zero, 73. A horizontal telegraph wire 0.5 kilometre, long running east and west is a part of a, circuit whose resistance is 2.5 ohm. The wire, falls to the ground from a heightof5 metres. If, g, 10.0 m/s and B = 2 x 105 Weber per, , metre, then the current induced in the, circuit is :, , (B) 0.02 ampere, (D) 0.04 ampere, , (A) 0.7 ampere, , (C) 0.01 ampere, , Ans. (B) 0.02 ampere, 74. An electron moves on a straight line path XY, as shown in fig. The abcd is a coil adjacent, to the path of electron. What will be the, direction of current if any current induced, in the coi?, , D) 3.6 Henry, , Henry, , SThe, , current passing through a choke coil, of 15 Henry is decreasing at the rate of 0.2, , ampere per second. The e.m.f. developed, across the coil:, , C, , X, , ELECTRON, , ., , Y

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(A) No current is induced, (B) abcd, , varies from, 2A in a time interval of, , in, 78. The electric current, , +2A to -, , a, , circuit, , 10s. Another coil of resistance 20 2 and, , C) adcb, , inductance 2H is placed near it. What will, , (D) The current will reverse direction as the, , be the induced currentin the second coil?, , electron goes past the coil, Ans. (B) abcd, 75. Fig. shows a straight wire, placed between, the pole pieces of a, magnet. Induced emf, will be developed across the ends of the, wire, when it is moved towards:, , (A) 4A, , (B) 8 A, , (C) 20 A, , (D) 40 A, , Ans. (D) 40 A, 79. The magnetic flux through a surface varies, with time as follows:, , 12t, , P, , WIRE, , Here, , +7t+3, , is in milliweber and t is in seconds., , What will be the induced emf at t= 5s ?, , (A) N, , (B) S, , (C)P, , (D) 2, , Ans. (C) P, 76. A conducting square loop of side L and, resistance R moves in a plane with uniform, velocity v perpendicular to one of its sides., A magnetic induction B, constant in time, , and space, pointing perpendicular and into, the plane of loop exists, everywhere. See fig., , The current induced in the loop is, , (A) 338 mV, , (B) 127 mV, , (C) 105 mV, , (D) None of these, , Ans. (B) 127 mV, 80. What is the energy stored in a coil of self, inductance 2H when a current of 10A is set, up through it?, , (A) 10J, C) 100J, , (B) 50J, (D) 500J, , Ans. (C) 100 J, 81. The current in a coil changes from, +10A to, -2A in 3 ms. What is the induced, emf in the, coil? The self inductance of the coil is 2 mH., (A) 8 V, , X, , X, , (A) BL clockwise, , (B) BL anticlockwise, C) 2BLanticlockwise, (D) zero, Ans. (D) zero, 77. The length of a solenoid is 20, cm, its area of, cross-section is 10 cm, and the number of, turns are 1000. Another coil of 500, turns is, wound in the middle. Their, coefficient of, mutual induction will be nearest to:, , (A), (C) 2 T, , Ans. (B) t, , (B) T, , (D) T2, , (B) 4V, (C) 0.8 V, (D) 0.4 V, Ans. (A) 8V, 82. A step-up transformer, raises the voltage, from 220V to 11000 V. If the number, of turns, of the, secondary be 1000, what is the number, of turns of the, primary?, (A) 2, (B) 20, (C) 200, Ans. (B) 20, , (D) 2000, , 83. What is the current, of the, , through the, , primary, transformer shown below?, , 230V, , coil, , 23V1152, , (A) 0.08 A, , (B) 0.04 A, , (C) 0.02 A, , (D) 0.01 A, Ans. (C) 0.02 A, 84. The distance between, the ends of the, of, , an, , aeroplane, , is 20m. The, , is, descending with, the horizontal, , a, , speed, , wings, aeroplane, 20 m/s. ., , of, of the earths, , component, magnetic field be 0.5 Gs, then what will be, the induced emf across the, , wings ?

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Ans., , (A) 40 mV, , (B) 20 mV, , (C) 10 mV, , (D) 5 mV, , (B), , 91. The magnetic flux linked with the coil is given, , as a function oftime =10f2 + 5t +5t + 10. At, , time t = 1s, what is the induced emf in the, coil?, (Diksha), , 20 mV, , 85. What will be the self inductance of a coil of, 100 turns if a current of 5 Ampere produces, a magnetic flux of 5 x 10 Wb ?, (A) 1 mH, , (B) 10 mH, , Ans., , (C) 1 uH, , (D) 10 uH, , 92., , (A) 30, , B) 40, , (C) -45, , (D) 45, , (C) - 45, , Eddy current can be minimised by using, (Diksha), , Ans. (A) 1 mH, , 86. There is a window 50 cm x 100 cm in a wal1, which is parallel to the magnetic meridian., The resistance of the window is 0.07 2. What, , is the induced charge when the window is, opened through 90°. Given that horizontal, component of earth's magnetic field is 0.35, Gs., , (B) 25 uC, , C) 250 HC, , (D) 2500 uC, , =, , (A) BAN, , (B) BAN sin ot, , (C) BAN cos ot, , (D) BAN ot, , What is the angular speed of rotation ?, (A) 4 rad/s, (B) 0.4 rad/s, , (C) 8 rad/Vs, , increased twice and the length is reduced, by 4, what will be the self inductance of the, coil?, , (Diksha), , (A) increased by 4, , Ans. (C) remains the samee, 95. A rectangular coil of, , (A) 25000V, , area 0.05 mis kept parallel, , uniform magnetic field of 2 T. What is, to, the flux linked with the, (Diksha), loop?, (A) 0.1, (B) 0.05, a, , (C) 1, , area, , 100, , cm having, , 500 turns rotates in a uniform magnetic field, of 0.5 T. The coil completes 500 rotation, per, , minute, calculate the instantaneous emf, , Ans. (D) 0.8 rad/s, , (D) zero, , C) 0V, , perpendicular, (Diksha), , (B) 2500V, (D) 500 V, , Ans. (C) OV, 96. In a three phase AC generator, between the, coils which is not the same?, (Diksha), , (A) phase difference between the voltages, , Ans. (D) zero, , (B) frequency of AC, of, , the, , +3j +3k., magnetic, , coil, , This coil, field of B, , is, is, =, , given, , kept, 4i +, , in, , as, , (C) number of turns, , a, , (D) speed of rotation, , 5j +6k., , What is the flux associated with the coil?, , C)45, Ans. (B) 12, , Ans. (D) current, 94. When the number of turns of the coil is, , when the plane of the coil is, to the magnetic field., , (D) 0.8 rads, , 89. A circular, loop of, , D) current, , (D) increased by 2, , 10 cm. It rotates in a magnetic field of 0.25, T and the maximum induced emf is 20 mV, , (A) 24, , (C) length, , (C) remains the same, , 88. A square loop of 10 turns has each side, , uniform, , 93. The self inductance is independent of, , (B) decreased by 4, , Ans. (C) BAN cos ot, , 3i, , Ans. (D) laminated sheets, , (A) number of turns (B) medium, , Ans. (C) 250 uC, 87. A square loop is rotating with angular speed, o about one of the diagonals as axis. At t, 0,, the plane of the loop is perpendicular to the, magnetic field B. If the number of turns of, the loop be N, then what is the instantaneous, flux through the coil ?, , A, , (C) thick sheets, (D) laminated sheets, , (Diksha), , (A) 2.5 4C, , 90. The area, , (A) thick wires, (B) thin sheets of metal, , (Diksha), , (B) 12, , (D) zeroo, , Ans. (A) phase difference between the voltages, 97. In a transformer, what cannot be stepped up, or down?, (Diksha), , (A) voltage, (C) charge, Ans. (D) power, , (B) current, , (D) power

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netic field. Therefore same emt is induced in, , Assertion-Reasoning Type 1Mark, , both the coils. But the induced current wil be, more in copper loop as its resistance will be, , O For below questions, two statements are, given-one labelled Assertion and the other, labelled Reason. Select the correct answer to, these questions from the codes (A), (B), (C), and (D) as given, (A) Both Assertion and Reason are true and, , below, , Reason is correct explanation of the, assertion., (B) Both Assertion and Reason are true but, Reason is not the correct explanation of, , lesser as compared to that of the aluminium, , loop., 4., , Assertion : An induced emf is generated, , when magnet is withdrawn from the sole., noid., , Reason: The relative motion between mag., emf., net and solenoid induces, , Ans. (A) Both Assertion and Reason are true and, , Reason is correct explanation of the, , assertion., , the assertion., , (C) Assertion is true but Reason is false., (D) Assertion is false but Reason is true., 1. Assertion: Faraday's laws are consequence, of conservation of energy., Reason: In a purely resistive AC circuit, the, current lags behind the emf in phase., , Ans. (B) Both Assertion and Reason are true but, Reason is not the correct explanation of, the assertion., , Explanation: Faraday's, , law is based on, the conversion of mechanical energy into, electrical energy. This is in accordance with, the law of conservation of energy. It is also, clearly known that in pure resistance, the emnf, is in phase with the current., , Explanation: Emf is induced when there is, a change in the magnetic flux., 5. Assertion : In the phenomenon of mutual, , induction, self induction of each of the coil, persists., , Reason: Self induction arises due to change, in current in the coil itself. In mutual induction, current changes in both the individual, coil., Ans. (A) Both Assertion and Reason are true and, , Reason is correct explanation of the, assertion., , Explanation: The self inductance of coilis, given by M = un-lA, , 2. Assertion: Lenz'slaw violates the principle, of conservation of energy., Reason: Induced emf always opposes the, change in magnetic flux responsible for its, , production., Ans. (D) Assertion is false but Reason is true., , Explanation Lenzd's law is based on conservation of energy and induced emf oppos, es the cause of it i.e., change in magnetic flux., , 3. Assertion, , Two identical loops, one of, , copper and another of aluminium are rotated with the same speed in the same magnetic, field. The emf induced in both the loop will, be same., Reason: The magnitude of induced emf is, directly proportional to the rate of change of, magnetic flux linked with the circuit., , Ans. (A) Both Assertion and Reason are true and, Reason is correct explanation of the, , assertion., , Explanation:Since, , both the loops are, , identical (same area and number of turns), and moving with a same speed in same mag, , 6. Assertion: Produced emf will always occur, whenever there is change in magnetic flux., Reason: Current always induces whenever, there is change in magnetic flux., , Ans. (C) Assertion is true but Reason is false., , Explanation: Emf will be induced only, there is change in magnetic flux. And, when,, the, current is inducade in closed, , loops., , 7. Assertion: When number of turns in a, , col15, , doubled, coefficient of self inductance of the, coil becomes 4 times., , Reason: As La N2, Ans. (A) Both Assertion and Reason, , are, , true an, , Reason is correct explanation of the, , assertion., Explanation:A L = HotN,, 2, , =4x HotN, , L'=Ho(2N)",, , 2, , 2, , 42

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A Assertion: When two coils are wound on, , been used in the construction of a, , coils is maximum., , (A) galvanometer, , Reason: Mutual induction does not depend, on, , orientation of, , the, , the coils., , Assertion and Reason are true and, Reason is correct explanation of the, , (A) Both, , Ans,, , (0) The laws of electromagnetic induction have, , each other the mutual induction between the, , (C) electric motor, D) generator, Ans. (D) generator, () What happens to the current in a coil while, , accelarating a magnet inside it ?, , assertion., , (A) increases, (B) decreases, (C) remains constant, , The inductance coils made of, will have very small ohmic resistance., , Explanation:, copper, , Due to change in magnetic flux a large, induced current will be produced in that, inductor which will oppose to the flow of, current., , 9. Assertion: Inductance coils, , are, , made of, , copper., , Reason Induced current is more in wire, Both Assertion and Reason are true but, Reason is not the correct explanation of, , (B), , (D) reverses, , Ans. (A) increases, Explanation: A charge in the magnetic, field induces an emf. When there is an emf., So there, has to be current. Hence, when the, magnet is moved inside a coil, the current in, it increases., , having less resistance., , Ans., , (iv) Emf can be induced by, (A) Change in the magnetic field only, , (B) Change in the area of cross-section only, , the assertion., , Explanation, , C) Change in angle between the magnetic, , Self inductance, , is the, property of virtue of which the coil opposes, in current flowing through it., the, , field and area only., , Case/Source Based Type, card, , ATM, , dedicated, , is, , 1 Mark, card, , payment, , a, , enables, , customer, , to, , which, their financial accounts via its and, the, others automated teller machines. When, then a, card is moved through a card reader,, one, in, flux is produced, in, , institution, , a, , access, , change, , magnetic, , direction, which induces emf, , or, , potential., , The current received by the pickup coil goes, and translated, , through signal amplification, into, , code. So that it is read, , binary, , Computer. This is how it, , field,, , area or, , Ans., , in the magnetic, angle between them., , field,, , area or, , (D) Change, , or, , financial, , payment card issued by a, , in the magnetic, angle between them., , (D) Change, , change, , 1. An, , by, , works., , Explanation:, , flux, , is the dot, , = BA cos 6, hence if either of the three, ie.,, the, magnetic field, area or angle changes,, emf will change, flux changes due to which, emf can be induced., , 2. Induction cooking heats a cooking vessel by, electrical induction, instead of by thermal, conduction from a flame, or an electrical, , 5513 D10, , 4000, , 12/20, , EISHA KRANRA, , Faraday's, , laws, , are, , a, , of the, , conservation of:, , (A) charge, (C) magnetic field, , Ans. (B) energy, , cooking, , vessel must, , induction cook top or "induction stove",, under the, coil of copper wire is placed, , an, , VISA, Gold, consequences, , element. The, , be made of or contain a ferromagnetic metal, such as cast iron or stainless steel. Heat is, this, coming from within the pan, making, In, method of cooking a lot more efficient., , Visa Gold, , 22239, , do, We, know that, dt, product of magnetic field, , emf =, , vector and area vector., , heating, , 20g, , (B) voltmeter, , vessel and, , cooking, , magnetic, , (B) energ8y, (D) Both (A) and (B), , an, , alternating, , electric, , current is passed through it. This oscillating, field wirelessly induces an electrical, , large eddy current, the heating of the vessel., , current in vessel. This, , flowing, , results in

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AEnhance your Answer, Calculate the, , in step by step manner,, , answer, , written, , with correct units., , is the phenomenon in, 3. Mutual inductance, which, , change, , (4), , Induction furnances, , are, , based, , on, , emf is induced in a coil, due to, of current in its neighbouring coil. The, , an, , mutual inductance phenomenon depends, on the position of 2 coils, their geometry, , the, , separation between them. This, induction of emf will takes place, as long as, in the neighbouring coil., the flux, , principle of, , and relative, , (A) Lenz law, , changs, , (B) Conduction, , (C) Electromagnetic Induction, (D) All of these, , Ans. (C) Electromagnetic Induction, , Explanation: By use of eddy currents, heating is done in the induction furnance., , (i), , (i) What does emf stand for ?, (A) Electronic magnetic force, B) Electromotive force, , The SI unit, , of mutual inductance is:, , (A) ohm, , (B) mho, , (C) Henry, , D), , (), , Mutual inductance of two coils, , D) Electromagnet force, , increased by:, , Ans. (B) Electromotive force, , (A) decreasing, , any source of electrical energy., (ii) Lenz law is a consequence of the law of, conservation of:, , the number of turns in the, , (B) increasing the number of turns in the, coils, , (C)winding the coils on wooden cores, Ans. (B) increasing the number of turns in the, , coils, , (C) induced emf, , Explanation : Mutual inductance of the, , D) induced current, , system is, , Ans. (B) energy, (iv) The magnetic flux threading a coil changes, , from 12 x 10-3 Wb to 6.0 x 10-3 wb in 0.01 s., Calculate the induced emf:, (A) 0.6 Wb/s, (B) 0.12 Wb/s, (C) 0.18 Wb/s, D) 0.3 Wb/s, Ans. (A) 0.6 Wb/s, , current in neighbouring coil is?, (A) zero, (B) infinity, (C) doubles, Ans. (A) zero, their is, , (6.0x10)-(12.0x103, , dt, , 0.01, , Wb/s, , M=Ho712 ta-L, , (ii) If the current in one coil becomes steady, the, , (D) halves, , Explanation Current is induced when, , Explanation:, =, , 0.6 V, , Mistakes to Avoid, Here, convert the number of turns in per meter, (stan-, , dard unit), , be, , (D) none of the above, , (A) charge, (B) energy, , 0.6, , can, , coils, , Explanation: It is a voltage developed by, , =, , of these, , Ans. (C) Henry, , (C) Electromagnetic force, , Ed, , none, , a, , changing magnetic flux., , (iv) Practical application of mutual inductance, is:, , (A), , DC, , generator, , (C) Transtormer, Ans. (C) Transformer, , (B) AC generator, D) Capacitor, , Explanation: It is advice, made of two or, more inductors, one of which is powered by, , inducing, AC,, inductor., , an, , AC voltage across the second

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m If the flux linkage in coil 1 is 3Wb and it, has 500 turns and the current in coil 2 is 2A,, calculate the mutual inductance, (A) 750 H, , (B) 500 H, , (C)450 H, , (D) 900 H, , Ans. (A), , Eddy, , are, , loops, , of electrical current, , magnetic field in the conductor according, Faraday's law of induction., , currents flow in closed, , within, conductors, in planes perpendicular to the, , loops, , magnetic field., , Eddy currents are useful in induction, heating, levitating, electromagnetic damping, , (), , on the, , (A) Induction, , (D) Air pressure, , induced within conductors by a changing, , Eddy, , set, , (C) Electromagnetic oscillations, , Explanation: M=3 x500/2 750 HH, 4., , up in the drum exert a torque, drum to stop the train. Identify:, , X, , (B) Eddy currents, , 750 H, , currents, , (1n), , and electromagnetic braking. They can be, minimized by adding slots in the conductor, surface and laminating., What is the heat generated in eddy current, operations?, (A) VI, , C) PRt, Ans. (D) 1PR, , B) VIR, , (D) PR, , The heat generated by this, Explanation:, method can be given by I4R, I is current and, , Ris the resistance., (i) Which of the following is not an application, of eddy currents?, , (A) Ammeter, , Ans. (B) Eddy currents, , Explanation, applied, , to the, , :, , A, , strong magnetic field is, , rotating drum attached, , to the, , wheel. The eddy currents set up in the drum, , exert a torque on the drum to stop the train., That is the reason eddy currents are set up 1n, , the drum of the train wheel., the law which is used to find out, the direction of eddy currents., (A) Lenz's law, , (iv) Identify, , (B) Faraday's law, , (C) Ampere Circuital law, (D) Maxwell's law, , Lenz's law, Explanation: Eddy currents also appose, , Ans. (A), , the change in magnetic flux, so their direction, , is given by Lenz's law., , (v) Eddy, , currents may not be, , suitable for, , electrostatic shielding., (A) True, , (B) False, , Ans. (B) False, the, Explanation: Electrostatic shielding istield, , practice of reducing the electromagnetic, in a space by blocking the field with barriers, , (B) Dead beat galvanometer, , made of conductive oil magnetic materials., , (C) Speedometer, , the conductivity of the sheet, used, the better the shielding of the transient, , (D) Energy meters, Ans. (A) Ammeter, , The, , higher, , magnetic field.