Question

A coil having n turns and resistance $4R\, O$. This combination is moved in time t seconds from a magnetic field $W_1$ weber to $W_2$ weber. The induced current in the circuit is

• A. $\frac{W_{2}-W_{1}}{5Rnt}$
• B. $\frac{\left(W_{2}-W_{1}\right)}{5Rt}$
• C. $\frac{W_{2}-W_{1}}{Rnt}$
• D. $\frac{n\left(W_{2}-W_{1}\right)}{Rt}$

Answer 1

Answer: (B)

$\frac{\left(W_{2}-W_{1}\right)}{5Rt}$

Answer 2

$I = \frac{n}{R' } \frac{d\phi}{dt}$ or, $I = - \frac{1}{R'}n\left[\frac{W_{2}-W_{1}}{t_{2}-t_{1}}\right]$ ($W_{1}$ and $W_{2}$ are not the magnetic field, but the values of flux associated with one turn of coil) $I = \frac{-1}{\left(R+4R\right)}\frac{n\left(W_{2}-W_{1}\right)}{t}$ or, $I = \frac{n\left(W_{2}-W_{1}\right)}{5Rt}$