Question

Magnetic flux passing through a coil changes with time as, $\varphi =10t^2+5t+1$ where $\varphi$ is in m wb and t in sec. then magnitude of emf at t = 5s is

• A. 0.105 V
• B. 0.01V
• C. 0.205V
• D. 1.2 V

Answer 1

The correct option is A 0.105 V

$\varphi =10t^2+5t+1$
$e=-\frac{d\varphi }{dt}=-[20t+5]\times {10}^{-3}$
where t = 5 sec
$e=-\left[\right(20\times 5)+5]\times {10}^{-3}$
$=-\left[0.105\right]V$
$e=0.105v$