Problem 1: Two identical coils A and B of 500 turns each has parallel planes such that 70% of flux produced by one coil links with the other. A current of 6 Amp flowing in coil A produces a flux of 0.06 Wb in it. If the current in coil A changes from 10 A to -10 A in .03 s, calculate (a) the mutual inductance and (b) the emf induced in coil B.

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Problem 2: A wheel with 12 metal spokes each 0.6 m long with a speed of 180 r.p.m in a plane normal to earth’s magnetic field at a place. If the magnitude of the field is 0.6 G, what is the magnitude of the induced emf between the axle and rim of the wheel.

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Problem 3: A circuit has 1000 turns enclosing a magnetic circuit 20 cm2 in section. With 4 A current, the flux density is 1 Wbm-2 and with 9 A current, it is 1.4 Wbm-2. Find the mean value of the inductance between these current limits and the induced emf if the current falls from 9 A to 4 A in 0.05 s.

Problem 4: A coil of resistance 100 ohms is placed in a magnetic field of 1 mWb. The coil has 100 turns and a galvanometer of 400 ohms is connected in series with it. Find the average emf and the current if the coil is moved is 1/10th from the given field to a field of 0.2 mWb.

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Problem 5: A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5 m/sec at right angle to the horizontal component of the earth’s magnetic field of 0.3 × 10-4 Wb/m2.

(a) What is the instantaneous emf induced in the wire?

(b) What is the direction of emf?

(c) Which end of the wire is at higher potential?

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Problem 6: Current in a circuit falls from 5.0 A to 0 A in 0.1 s. If an average emf of 200 V induced, give an estimate of the self-inductance of the circuit?

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Problem 7: A long solenoid with 15 turns / cm has a small loop of area 2.0 cm2 placed inside the solenoid normal to its axis. If the current created by the solenoid changes steady from 2.0 A to 4.0 Amp in 0.1 s. What is the induced emf in the loop when the current is changing.

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Problem 8: A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cms-1 in a direction normal to (a) longer side (b) shorter side of the loop? For how long does the induced voltage lasts in each case?

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Problem 9: A 90 mm length of wire moves with an upward velocity of 35 m/s between the poles of a magnet. The magnetic field is 80 mT directed to the right. If the resistance in the wire is 5.00 m ohms, what are the magnitude and direction of the induced current?

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Problem 10: 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 flux linkage with the other coil?

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Problem 11: The back emf in a motor is 120 V when the motor is turning at 1680 rev/min. What is the back emf when the motor turns at 3360 rev/min?

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