JEE MainPhysicsAlternating CurrentMCQ+4 / −1
In a series circuit and the voltage and the frequency of the main supply is and respectively. On taking out the capacitance from the circuit the current lags behind the voltage by On taking out the inductor from the circuit the current leads the voltage by The power dissipated in the circuit is
- A
- B
- C
- D
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Correct answer: D
- Given data
- Resistance:
- Supply voltage:
- Frequency:
We need the power dissipated in the series circuit.
For a series circuit, where is the phase angle of the complete circuit.
- Case 1: Capacitor removed
Then the circuit becomes a series circuit.
Given: current lags voltage by . For an circuit, So, Hence,
- Case 2: Inductor removed
Then the circuit becomes a series circuit.
Given: current leads voltage by . For an circuit, (using magnitude of phase angle) Thus, Hence,
- Now consider the complete circuit
Net reactance in series circuit is But here, So,
Therefore the circuit is in resonance, and the impedance is purely resistive:
Hence current is
- Power dissipated
Since the circuit is purely resistive at resonance, Therefore,
- Option check
- A: — incorrect
- B: — incorrect
- C: — incorrect
- D: — correct
Final Answer:
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