Answer
$4.2\times10^{-2}volts$
Work Step by Step
The magnitude of the average induced emf is calculated using equation 21–2a.
$$|\epsilon|=\frac{|\Delta \Phi_B|}{\Delta t}$$
$$=\frac{|\pi(0.054m)^2(-0.25T-0.48T) |}{0.16s}$$
$$=4.2\times10^{-2}volts$$
