Question

A current passing through a coil of self-inductance of $2mH$ changes at the rate of $20mA{s}^{-1}$. The emf induced in the coil is

• A. $10\mu V$
• B. $40\mu V$
• C. $10mA$
• D. $40mA$

Answer 1

The correct option is B

$40\mu V$

Step 1: Given Data:

Self inductance of coil, $L=2mH$

$=2\times {10}^{-3}H$

Rate of change of current, $\frac{di}{dt}=20mA{s}^{-1}$

$=20\times {10}^{-3}A{s}^{-1}$

Step 2: Formula used:

$e=L\frac{di}{dt}$

Where, $e=$emf induced

$L=$Self inductance

$\frac{di}{dt}=$rate of change of current

Step 3: Calculating the induced emf:

$e=2\times {10}^{-3}\times 20\times {10}^{-3}$

$=40\times {10}^{-6}A$

$=40\mu A$

Hence, option D is the correct answer.