Question

A hundred turns of insulated copper wire are wrapped around an iron cylinder of area $1\times {10}^{-3}{m}^2$ and are connected to a resistor. The total resistance in the circuit is 10 ohms. If the longitudinal magnetic induction in the iron changes from 1 weber $m^{-2}$, in the direction to 1 Weber $m^{-2}$ in the opposite direction, how much charge flows through the circuit

• A. $2\times {10}^{-2}C$
• B. $2\times {10}^{-3}C$
• C. $2\times {10}^{-4}C$
• D. $2\times {10}^{-5}C$

Answer 1

The correct option is A $2\times {10}^{-2}C$

$dQ=\frac{d\varphi }{R}=\frac{nAdB}{R}$

$Q=\frac{nA\Delta B}{R}=\frac{100\times 1\times {10}^{-3}\times 2}{10}=2\times {10}^{-2}C$