Question

In a magnetic field of $0.05\, T,$ area of a coil changes from $101\, cm^2$ to $100\, cm^2$ without changing the resistance which is $2\,\Omega$. The amount of charge that flow during this period is

• A. $2.5 × 10^{-6}\, C$
• B. $2 × 10^{-6}\, C$
• C. $10^{-6}\,C$
• D. $8 × 10^{-6}\, C$

Answer 1

Answer: (A)

Magnetic Flux, $\phi=B\cdot A$
Change in flux, $d\,\phi=B\cdot dA$
$=0.05\left(101-100\right)\times10^{-4}$
$=5\times10^{-6}\,Wb$
Charge $dQ=\frac{d\phi}{R}$
$=\frac{5\times10^{-6}}{2}=2.5\times10^{-6}\,C$