Question

The flux associated with coil changes from $1.35Wb$ to $0.79Wb$ within $\frac{1}{10}s$. Then the charge produced by the earth coil, if resistance of coil is $7\Omega$ is:

• A. $0.08C$
• B. $0.8C$
• C. $0.008C$
• D. $8C$

Answer 1

The correct option is A $0.08C$

As, $I=\frac{E}{R}=\frac{d\varphi }{Rdt}$
or $Idt=\frac{d\varphi }{R}$
Integrating
$\int Idt=\int \frac{d\varphi }{R}$
or, $q=\frac{\varphi }{R}$
If coil contains $N$ turns, then $q=\frac{N\varphi }{R}$
If there is flux change $\Delta \varphi$, then
$q=\frac{N\Delta \varphi }{R}$
$=\frac{1}{7}\times (1.35-0.79)$
$=0.08C$