Question

A coil with an area of $0.50m^2$ and a resistance of 7 ohms is completely in a changing magnetic field.
If the current in the coil is 2.0 Amps, what is the rate of change of the magnetic field?

• A. $3.5T/s$
• B. $7T/s$
• C. $14T/s$
• D. $28T/s$

Answer 1

The correct option is D $28T/s$

Given : $R=7$ $\Omega$ $A=0.50$ $m^2$ $I=2.0$ $A$

Thus emf in the coil $E=IR=2.0\times 7=14.0$ volts

Also emf in the coil $E=\frac{d\left(BA\right)}{dt}=A\frac{dB}{dt}$

$\therefore$ $14.0=0.50\times \frac{dB}{dt}$

$⟹\frac{dB}{dt}=28$$T/s$