Question

A circular loop in the plane of the paper lies in a 0.70 TT magnetic field pointing into the paper.

a. If the loop's diameter changes from 23.6 cmcm to 9.0 cmcm in 0.48 ss , what is the direction of the induced current?

b. What is the magnitude of the average induced emf?

Answer 1

a) according to Lenz law , which states that the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field.

so the current induced is to the right

b) emf = rate of change of magnetic flux

= d $\phi$ / dt

= d(BA) / dt

= B dA/dt

= 0.7*pi / 4 * ( 0.236^2 - 0.09^2 ) / 0.48

= 0.0545 V

so the magnitude of average emf induced is 0.0545 V