Question

A circular loop in the plane of the paper lies in a 0.65 T magnetic field pointing into the paper. If the loop's diameter changes from 19.4 cm to 7.2 cm in 0.15 s , what is the direction of the induced current? What is the magnitude of the average induced emf? If the coil resistance is 3.3 ? , what is the average induced current?

Answer 1

here,

magnetic feild , B = 0.65 T

intial diameter , d1 = 19.4 cm = 0.194 m

final diameter , d2 = 7.2 cm = 0.072 m

time taken , t = 0.15 s

as the feild is into the paper

and the area of the loop is decreased

the flux through the loop is decreased

using Lenz's law

the induced current is so that the flux is incraesed

so, the induced current is CLOCKWISE

the induced EMF , V = d(flux)/dt

V = pi * 0.65 * ((0.194/2)^2 - (0.072/2)^2 )/0.15 V

V = 0.11 V

the induced current , I = V/R

I = 0.11 /3.3 A

I = 0.03 A