In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value

The correct answer is: A. Will change the maximum value of current at resonance.

In a series resonant circuit, the current is maximum at resonance. The resonance frequency is determined by the inductance and capacitance of the circuit. When the inductance is increased to twice its value and the capacitance is reduced to half its value, the resonance frequency will remain the same. However, the impedance at resonance will decrease, and the maximum value of current will increase.

Here is a more detailed explanation of each option:

• Option A: Will change the maximum value of current at resonance. This is correct because the current is maximum at resonance. When the inductance is increased to twice its value and the capacitance is reduced to half its value, the resonance frequency will remain the same. However, the impedance at resonance will decrease, and the maximum value of current will increase.
• Option B: Will change the resonance frequency. This is incorrect because the resonance frequency is determined by the inductance and capacitance of the circuit. When the inductance is increased to twice its value and the capacitance is reduced to half its value, the resonance frequency will remain the same.
• Option C: Will change the impedance at resonance frequency. This is correct because the impedance at resonance is determined by the inductance and capacitance of the circuit. When the inductance is increased to twice its value and the capacitance is reduced to half its value, the impedance at resonance will decrease.
• Option D: Will increase the selectivity of the circuit. This is incorrect because the selectivity of the circuit is determined by the Q factor of the circuit. The Q factor is a measure of how sharply the impedance of the circuit changes at resonance. When the inductance is increased to twice its value and the capacitance is reduced to half its value, the Q factor will decrease, and the selectivity of the circuit will decrease.