Question

A solenoid has 2000 turns wound over a length of 0.30 metre. The area of its cross-section is . Around its central section, a coil of 300 turns is wound. If an initial current of 2 A in the solenoid is reversed in 0.25 sec, then the e.m.f. induced in the coil is

• A. $6\times {10}^{-4}$V
• B. $4.8\times {10}^{-3}$ V
• C. $6\times {10}^{-2}$V
• D. 48 mV

Answer 1

The correct option is D

48 mV

Induced emf e= $M\frac{di}{dt}=\frac{{\mu }_0{N}_1{N}_{2}A}{l}.\frac{di}{dt}$
$=\frac{4\pi \times {10}^{-7}\times 2000\times 300\times 1.2\times {10}^{-3}}{0.30}\times \frac{|2-(-2)|}{0.25}$
$=48.2\times {10}^{-3}V=48mV$