Physics - EMI/AC Question with Solution | TestHub

The magnetic flux through the loop is $\Phi =BA=B(\pi r^2)$. The induced EMF is given by Faraday's law as $\text{EMF}=|-\frac{d\Phi }{dt}|=|-\frac{d}{dt}(B\pi r^2)|=B\pi (2r)\frac{dr}{dt}$. Given $B=0.2\text{ T}$, $r=20\text{ cm}=0.2\text{ m}$, and $\frac{dr}{dt}=2\text{ cm/s}=0.02\text{ m/s}$.$\text{EMF}=(0.2\text{ T})\times \pi \times (2\times 0.2\text{ m})\times (0.02\text{ m/s})=0.0016\pi \text{ V}\approx 0.0016\times 3.14159\text{ V}\approx 0.005026\text{ V}$. Converting to millivolts, $\text{EMF}\approx 5.026\text{ mV}$. Rounding to the nearest integer gives 5.