Question

A 40-turn coil has a diameter of 17 cm. The coil is placed in a spatially uniform magnetic field of magnitude 0.40 T so that the face of the coil and the magnetic field are perpendicular. Find the magnitude of the emf induced in the coil (in V) if the magnetic field is reduced to zero uniformly in the following times.

Answer 1

Complete question:

A 40-turn coil has a diameter of 17 cm. The coil is placed in a spatially uniform magnetic field of magnitude 0.40 T so that the face of the coil and the magnetic field are perpendicular. Find the magnitude of the emf induced in the coil (in V) if the magnetic field is reduced to zero uniformly in the following times.  (a) 0.10 s, (b) 1.0 s, and (c) 60 s.

Answer:

(a) E = 3.632 V

(b) E = 0.3632  V

(c) E = 6.053 mV

Explanation:

Given;

number of turn of the coil, N = 40 turn

diameter of the coil, d = 17 cm = 0.17 m

radius of the coil, r = d /2 = 0.17 /2 = 0.085 m

initial magnitude of magnetic field, B₁ = 0.4 T

final magnitude of magnetic field, B₂ = 0

The induced emf in the coil is given by;

$E = -N\frac{dB}{dt} A = \frac{-NA(B_2 - B_1)}{dt} =\frac{NA(B_1-B_2)}{dt} =\frac{NAB_1}{t}$

A is area of the coil = πr² = π(0.085)² = 0.0227 m²

(a) when the time is 0.1 s

$E= \frac{40*0.0227*0.4}{0.1} = 3.632 \ V$

(b) when the time is 1 s

$E = \frac{40*0.0227*0.4}{1} \\\\E = 0.3632 \ V$

(c) when the time is 60 s

$E = \frac{40*0.0227*0.4}{60} \\\\E = 6.053 \ mV$