A magnetic field of 2 × 10^–2 T acts at right angles to a coil of area 100 cm² with 50 turns. If the average emf induced in the coil is 0.1V when it is removed from the field in time t. The value of ‘t’ is 
 

Given data: A coil having a surface area of $100 {\mathrm{cm}}^2\text{ and }50\text{ turns }$is affected at right angles by a magnetic field of $2\times {10}^{-2} \text{T}$. The coil experiences an average induced emf of 0.1 v. 

Concept used: Electromagnetic induction. 

Detailed solution:

   $e=N\frac{d\varphi }{dt}$ 

  $\varphi =\left(2\times {10}^{-2}\right)\left(100\times {10}^{-4}\right)$

  $e=N\frac{\left(2\times {10}^{-2}\right)\left(100\times {10}^{-4}\right)}{t}$ 

 &$0.1=50\times 2\times {10}^{-2}\times 100\times {10}^{-4}/\mathrm{t}$

 $\mathrm{t}=\frac{{10}^{+4}\times {10}^{-4}\times {10}^{-2}}{0.1}=0.1\text{sec}$