Question

A coil of copper having $1000$ turns is placed in a magnetic field $(B=4\times {10}^{-5})T$ perpendicular to its axis. The cross sectional area of the coil is $0.05m^2$. If it turns through ${180}^o$ in $0.01$ second, then the e.m.f. induced in the coil will be

• A. $4V$
• B. $0.04V$
• C. $0.4V$
• D. $0.2V$

Answer 1

The correct option is C $0.4V$

Flux passing through the coil, $=1000\times 4\times {10}^{-5}\times 0.05=2\times {10}^{-3}$ weber

Change in flux when the coil turns by ${180}^o$.

$=2\times {10}^{-3}-(-2\times {10}^{-3})$

$\Delta \varphi =4\times {10}^{-3}$

e.m.f.$=\frac{d\varphi }{dt}=\frac{4\times {10}^{-3}}{0.01}=0.4V$