Question

What is the average emf induced in a circular wedding ring of diameter 2.2 cm if the ring is at the center of the MRI magnet coils and the original magnetic field is perpendicular to the plane that is encircled by the ring

Answer 1

Missing information

Consider a superconducting MRI magnet for which the magnet field decreases from 8.0 T to nearly 0 in 20 s

Answer:

0.152 mV

Explanation:

Change in magnetic field, dB=8-0=8 T

Time interval, dt=20 s

Diameter of ring= 2.2cm hence radius is 1.1 cm equivalent to 0.011

$\epsilon=nA\frac {dB}{dt}$ where n is the number of terms and for this question n=1 and A is area which is given by $\pi r^{2}$ hence

$\epsilon=n\pi r^{2} \frac {dB}{dt}$ and substituting the values  

$\epsilon=1\pi 0.011^{2}\times \frac {8}{20}=1.52\times 10^{-4} V=0.152 mV$

Therefore, induced emf is 0.152 mV