Question

When current in a coil changes at a steady rate from 8 A to 6 A in 4 ms, an emf of 1.5 V is induced in it. The value of self-inductance of the coil is :

• A. 6 mH
• B. 12 mH
• C. 3 mH
• D. 9 mH

Answer 1

The Correct Option is C

The induced emf (E) in a coil is related to the rate of change of current by the formula:

Formula for induced emf:
\( E = -L \frac{\Delta I}{\Delta t} \)

where:

• E = 1.5 V is the induced emf
• L is the self-inductance
• \(\Delta I\) = 8 - 6 = 2 A is the change in current
• \(\Delta t\) = 4 ms = \( 4 \times 10^{-3} \) s is the time interval

Rearranging the formula to solve for L:

Rearranged formula:
\( L = \frac{E \Delta t}{\Delta I} \)

Substituting the given values:

\( L = \frac{(1.5)(4 \times 10^{-3})}{2} = 3 \times 10^{-3} \, \text{H} = 3 \, \text{mH} \)