Question

A solenoid has 2000 turns wound over a length of 0.30 metre. The area of its cross-section is 1.2 × 10^–3m². Around its central section, a coil of 300 turns is wound. If an initial current of 2A in the solenoid is reversed in 0.25 sec, then the emf induced in the coil is

• A. 6 × 10^–4V
• B. 4 × 10^–3V
• C. 6 × 10^–2V
• D. 48 Mv

Answer 1

Answer: (D)

48 Mv

Answer 2

By using $M = \frac{\mu_{0}N_{1}N_{2}A}{l}$ and $|e| = M\frac{di}{dt}$;

$M = 3.01 \times 10^{- 3}H$ ⇒ $e = 3.01 \times 10^{- 3} \times \frac{\{ 2 - ( - 2)\}}{0.25}$;

$e = 48mV.$