﻿ A wheel with 10 spokes each of length L m is rotated with a uniform angular velocity ω in a plane normal to the magnetic field B. The emf induced between the axle and the rim of the wheel is | Electromagnetic Induction

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# Electromagnetic Induction

#### Multiple Choice Questions

41.

Two concentric coils each of radius equal to 2 $\mathrm{\pi }$ cm are placed at right angles to each other. If 3A and 4A are the currents flowing through the two coils respectively. The magnetic induction (in Wb m-2) at the centre of the coils will be

• 5 × 10-5

• 12 × 10-5

• 7 × 10-5

• 10-5

42.

Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to the equation I = im sin ωt, where im = 10 A and ω = 100 rad s-1. The maximum value of the emf induced in the second coil is

• $\mathrm{\pi }$

• $2\mathrm{\pi }$

• $4\mathrm{\pi }$

• $5\mathrm{\pi }$

# 43.A wheel with 10 spokes each of length L m is rotated with a uniform angular velocity ω in a plane normal to the magnetic field B. The emf induced between the axle and the rim of the wheel is ${\mathrm{\omega BL}}^{2}$ NωBL2

B.

Number of spokes is immaterial as the emf's across the spokes are in parallel.

From Faraday's laws, induced emf in wheel between axle and rim is given by the following formula.

44.

When 100 V DC is applied across a coil, a current of 1 A flows through it. When 100 V AC of50 Hz is applied to the same coil only 0.5 A flows. The inductance of the coil is

• 5.5 mH

• 0.55 mH

• 55 mH

• 0.55 H

45.

An aluminium ring B faces an electromagnet A. The current I through A can be altered. Then which of the following statements is correct ?

• If I decreases, A will repel B

• Whether I increases or decreases, B will not experience any force

• If I increases, A will repel B

• If I increases, A will attract B