Question

In the following figure, the magnet is moved towards the coil with a speed $v$ and induced emf is $e$. If magnet and coil recede away from one another each moving with speed $v$, the induced emf in the coil will be

• A. e
• B. 2 e
• C. e / 2
• D. 4 e

Answer 1

Answer: (B)

${\left(\frac{d\varphi }{dt}\right)}_{\text{In first case }}=e$
${\left(\frac{d\varphi }{dt}\right)}_{\text{relative velocity }2v}=2{\left(\frac{d\varphi }{dt}\right)}_{Icase}=2e$