🛠️ JEE🧲 Physics

Alternating Current

2 solved JEE Physics previous year questions on Alternating Current, each with the correct answer and a full explanation.

To increase the resonant frequency in series LCR circuit,

aSource frequency should be increased.

bAnother resistance should be added in series with the first resistance.

cAnother capacitor should be added in series with the first capacitor.

dThe source frequency should be decreased.

✓ Correct answer: c) Another capacitor should be added in series with the first capacitor.

ExplanationOn decreasing , frequency would increase therefore, another capacitor should be added in series with the first capacitor.

Given below are two statements: Statement I: When the frequency of an a.c. source in a series LCR circuit increases, the current in the circuit first increases, attains a maximum value and then decreases. Statement II: In a series LCR circuit, the value of power factor at resonance is one. choose the most appropriate answer from the options given below:

aStatement-I is incorrect but statement-II is correct.

bBoth statement-I and statement-II are incorrect.

cStatement-I is correct but statement-II is incorrect.

dBoth statement-I and statement-II are correct.

✓ Correct answer: d) Both statement-I and statement-II are correct.

ExplanationIn the series of RLC circuit – At resonance, XL = XC Impedance is minimum so the current will be maximum, from the figure if f is increase the impedance also increase then current decrease, so statement (I) is correct.In RLC circuit at resonance, XL = XC So, the circuit behaves as pure resistive circuit the power factor will be unit so statement II is also correct.

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