A small signal voltage ${\rm{V(t)}}\,{\rm{ = }}\,{{\rm{V}}_{\rm{0}}}{\rm{sin}}\,{\rm{\omega t}}$ is applied across an ideal capacitor C:

Current I (t), legs voltage V (t) by ${90^{\rm{o}}}$

Current I (t) is in phase with voltage V (t).

Current I (t) leads voltage V (t) by ${180^{\rm{o}}}$

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JEE • PHYSICS • ALTERNATING CURRENT

Alternating current practice · Mixed difficulty

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Practice format and chapter quiz

These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 271-279 of 279 questions

271 Medium

271 of 279

Understanding +4 | -1

An LCR series circuit is connected to a source of alternating current. At resonance, the applied voltage and the current flowing through the circuit will have a phase difference of

View answer and explanation

Correct option: D

0

Option D (

0

) is correct because at resonance, the inductive and capacitive reactances cancel each other out, resulting in a purely resistive circuit with zero phase difference.

272 Easy

272 of 279

Remembering +4 | -1

Transformer works on the principle of

View answer and explanation

Correct option: A

Mutual induction between two coils

Option A (Mutual induction between two coils) is correct because a transformer operates based on the principle of mutual induction, where a changing magnetic field in one coil induces a voltage in another coil.

273 Medium

273 of 279

Analyzing +4 | -1

Assertion: In LR Circuit ohm's law is not obeyed at every instant.

Reason: Current always lags from voltage.

View answer and explanation

Correct option: D

If both Assertion & Reason are false

Option D (If both Assertion & Reason are false) is correct because Ohm's law is applicable instantaneously in LR circuits, and the current lags the voltage in an LR circuit.

274 Medium

274 of 279

Application +4 | -1

An inductor of inductance

100 \mathrm{~mH}

is connected in series with a resistance, a variable capacitance and an AC source of frequency

2.0 \mathrm{~kHz}

. What should be the value of the capacitance so that maximum current may be drawn into the circuit?

View answer and explanation

Correct option: A

63 \mathrm{~nF}

Option A (63 nF) is correct because maximum current is drawn at resonance, where the capacitive reactance equals the inductive reactance, leading to

C = \frac{1}{\omega^2 L}

275 Medium

275 of 279

Understanding +4 | -1

Assertion: The average value of alternating emf is

63.39 \%

of the peak value.

Reason:The rms value of alternating emf is

70.72 \%

of peak value.

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Correct option: B

If both assertion and reason are true and reason is not correct explanation of assertion.

Option B (If both assertion and reason are true and reason is not correct explanation of assertion) is correct because both the average and RMS values are related to the peak value, but the RMS value doesn't directly explain the average value.

276 Medium

276 of 279

Understanding +4 | -1

Mark the correct statement.

View answer and explanation

Correct option: A

Ideal inductor does not dissipate power in an AC circuit

Option A (Ideal inductor does not dissipate power in an AC circuit) is correct because the average power dissipated by an ideal inductor over a complete cycle is zero.

277 Medium

277 of 279

Understanding +4 | -1

A small signal voltage

\mathrm{V(t)}\,\mathrm{ = }\,{\mathrm{V}_\mathrm{0}}\mathrm{sin}\,\mathrm{\omega t}

is applied across an ideal capacitor C:

View answer and explanation

Correct option: B

Over a full cycle the capacitor C does not consume any energy from the voltage source

Option B (Over a full cycle the capacitor C does not consume any energy from the voltage source) is correct because the energy stored in a capacitor during charging is released during discharging, resulting in zero net energy consumption over a cycle.

278 Medium

278 of 279

Analyzing +4 | -1

Assertion: A bulb connected in series with a solenoid is connected to ac source. If a soft iron core is introduced in the solenoid, the bulb will glow brighter.

Reason: On introducing soft iron core in the solenoid, the inductance increases.

View answer and explanation

Correct option: D

If assertion is false but reason is true.

Option D is correct because the assertion is false (bulb glows dimmer), but the reason is true (inductance increases).

279 Medium

279 of 279

Understanding +4 | -1

Statement (A): When frequency is greater than resonance frequency in a series LCR circuit, it will be an inductive circuit.

Statement (B): Resultant voltage will lead the current in LR circuit.

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Correct option: A

Both (A) and (B) are true

Option A is correct because in a series LCR circuit, when the frequency is greater than the resonance frequency, the circuit behaves inductively, and in an LR circuit, the voltage leads the current.

Revision notes and key takeaways

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