Physics - EMI/AC Question with Solution | TestHub

In the r-t graph, it is clear that from a to b there is no change in radius and hence no change in area and magnetic flux. Same is the situation from c to d for b to c.

$\text{Now}\text{,}\left|\text{e}\right|=\frac{\text{d}}{\text{dt}}\left(\varphi \right)$

$\left|\text{e}\right|=\text{B}\frac{\text{d}}{\text{dt}}\left(\pi {\text{r}}^2\right)=\text{B}\pi 2\text{r}\frac{\text{dr}}{\text{dt}}$

$\text{Since r}\propto \text{t,}\therefore \frac{\text{dr}}{\text{dt}}=\text{constant}$

∴$\left|\text{e}\right|\propto \text{r}$

This is represented in option (2).