Question 154: AC fundamentals

Question

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.
In the light of given statements, choose the most appropriate answer from the options given below.

Accepted Answer

Statement I
is true because in a series LCR circuit, the current first increases as the frequency increases, reaching a maximum value when the circuit is at resonance. At resonance, the inductive reactance (XL) and capacitive reactance (XC) cancel each other out, resulting in the lowest impedance (Z) and the highest current. As the frequency continues to increase beyond resonance, the current in the circuit decreases.
Statement II
is also true because, at resonance in a series LCR circuit, the inductive reactance (XL) and capacitive reactance (XC) are equal and cancel each other out. This results in the impedance (Z) being purely resistive. The power factor at resonance is given by the cosine of the phase angle (ÃÂ¸), and since the phase angle is 0ÃÂ° at resonance, the power factor is 1.
Thus, both statements are true, and the correct answer is Both Statement I and Statement II are true.

Answer

Both Statement I and Statement II are False.

Answer

Statement I is incorrect but Statement II is true.

Answer

Both Statement I and Statement II are true.

Answer

Statement I is correct but Statement II is false.

AC fundamentals

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