Question

When a coil of 100 turns and resistance 0.5 $\Omega$ is moved towards a stationary magnet, the magnetic flux linked with the coil changes from 5 x ${10}^{-2}$ weber to 0.15 weber. Find the charge flowing through the coil during its motion

• A. 80 C
• B. 40 C
• C. 20 C
• D. 60 C

Answer 1

The correct option is C 20 C

(e) = emf induced in the coil is $=n\frac{d\varphi }{dt}$

where n = no of turns of coil

$\varphi$ = flux.

$e=-n\frac{(0.15-0.05)}{dt}=\frac{-100\times 0.1}{dt}=\frac{-10}{dt}$

I = current through coil $=\frac{\left|e\right|}{R}=\frac{10}{0.5dt}=\frac{20}{dt}$

$I=\frac{d\varphi }{dt}$

where $\varphi$ = change flowing through coil

$d\varphi =Idt\varphi =Idt=20\varphi =20C$