NEETPhysicsAlternating Current
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): A light bulb connected in series with an ideal inductor glows brighter when connected to a DC source than when connected to an AC source of the same rms voltage. Reason (R): The inductive reactance of an ideal inductor is zero for direct current, leading to a lower total impedance in the circuit. I
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
For a DC source, the frequency f = 0 , so the inductive reactance X_L = 2 f L = 0 . The total impedance of the circuit is simply the resistance of the bulb ( Z = R ). For an AC source, the frequency f > 0 , so the inductor offers a non-zero reactance X_L . The total impedance of the circuit becomes Z = R^2 + X_L^2 , which is greater than R . Since the rms voltage is the same in both cases, the current drawn from the DC source ( I = V R ) is greater than the rms current drawn from the AC source ( I_ rms = V Z ). The