Question

The current in a coil changes from 50A to 10A in 0.1 second. The self-inductance of the coil is 20H. The induced e.m.f. in the coil is:

• A. 800V
• B. 6000V
• C. 7000V
• D. 8000V

Hint:

The induced e.m.f. is directly related to the rate of change of current. A faster change in current results in a larger induced voltage.

Answer 1

The Correct Option is D

Step 1: According to Faraday's law of electromagnetic induction, the induced electromotive force (e.m.f.) in a coil is given by: \[ \mathcal{E} = -L \frac{dI}{dt}. \] Step 2: Given the values \( L = 20H \), \( dI = 50A - 10A = 40A \), and \( dt = 0.1s \), we calculate: \[ \mathcal{E} = - (20) \times \left( \frac{40}{0.1} \right) = 8000V. \]