Question

Current in Ampere in an inductor is given by 10 + 10 t where t is the time in seconds. If the self- induced emf in the coil is 20 mV, then its self- inductance is:
1. 10 mH
2. 1 mH
3. 2 mH
4. 20 mH

Answer 1

Correct Answer - Option 3 : 2 mH

Concept:

Self-inductance: Self-inductance is the phenomenon where a current-carrying coil resists the change in the current flowing through it.

• ​The resistance to the change in current is due to the induced emf in the coil. 
• The direction of the induced emf is opposite to the applied voltage if the current is increasing and the direction of the induced emf is in the same direction as the applied voltage if the current is decreasing.
• The unit of inductance is Henry (H).
• The induced emf is given by the formula,  \(e = L\frac{{di}}{{dt}}\)

 

Calculation:

i = 10 +10 t

di/dt = 10

e = L × di/dt

20 × 10^-3 = L × 10

L = 2 mH