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The time taken for the magnetic energy to reach 25% of its maximum value, when a solenoid of resistance R, inductance L is connected to a battery, is:
- (L/R) ln5
- infinite
- (L/R) ln2
- (L/R) ln10
Correct answer: (L/R) ln2
Solution
The time taken for the magnetic energy to reach a certain percentage of its maximum value in an RL circuit is derived from the exponential growth of current. At 25% of maximum energy, the relationship simplifies to (L/R) ln2, which reflects the time constant of the circuit.
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