Question

In a coil, an increase in current from 5 A to 10 A in 100 ms induces an emf of 100 V. The self-inductance of the coil is:

• A. 2 H
• B. 10 H
• C. 20 H
• D. 2000 H

Answer 1

Answer: (A)

2 H

Answer 2

$\text{ The induced emf } \varepsilon \text{ in a coil is related to the self-inductance } L \text{ by the formula:}\\\\$

$\varepsilon = L \frac{dI}{dt}$

$\text{where } \frac{dI}{dt} \text{ is the rate of change of current. In this case, } \frac{dI}{dt} = \frac{10 - 5}{0.1} = 50 \, \text{A/s}.\\\\$
$\text{Substituting the values:}\\\\$
$100 = L \times 50 \quad \Rightarrow \quad L = \frac{100}{50} = 2 \, H$
$\text{Thus, the self-inductance is } 2 \, H.$