Answer
$emf=3.2mV$
Work Step by Step
We know that;
$emf=\frac{d\phi}{dt}$
This can be rewritten as:
$emf=AB\omega$
The formula can further be written as:
$emf=(\frac{\pi r^2}{2})(B)(2\pi f)$
We plug in the known values to obtain:
$emf=(\frac{3.1416\times (0.02)^2}{2})(0.020)(2\times 3.1416\times 40)$
$emf=3.2\times 10^{-3}=3.2mV$
