Question

A circular coil of radius $0.1m$ has $80$ turns of wire. If the magnetic field through the coil increases from $0to2$ tesla in $0.4s$ and the coil is connected to a $11\Omega$ resistor, what is the current flow through the resistor during the 0.4 s?

• A. $\left(\frac{8}{7}\right)A$
• B. $\left(\frac{7}{8}\right)A$
• C. 8 A
• D. 7 A

Answer 1

Answer: (A)

$\left|\epsilon \right|=N\frac{d\varphi }{dt}=NA\frac{dB}{dt}$
$=80\times \frac{22}{7}\times {\left(0.1\right)}^2\left(\frac{2.0}{0.4}\right)$
$I=\frac{|\epsilon |}{R}=80\times \frac{22}{7}\times \frac{{\left(0.1\right)}^2\times 5}{11}=\frac{8}{7}A$