Q144 / 150 · MHT CET 2025 (23 Apr Shift 2) · Physics

Same current is flowing in two different a.c. circuits. First circuit contains only inductance and second contains only capacitance. If the frequency of a.c. is increased in both circuits, the current will

  • A
    increase in the first circuit and decrease in second.
  • B
    increase in both circuits.
  • C
    decrease in both circuits.
  • Correct answer
    D
    decrease in first circuit and increase in second.

Solution

The behavior of current with changing frequency depends on the circuit's reactive components.

For a purely inductive circuit, the inductive reactance is $X_L = 2\pi fL$. Applying Ohm's law, the current becomes $I_L = V/X_L = V/(2\pi fL)$. Since $f$ appears in the denominator, increasing the frequency causes the current to decrease.

For a purely capacitive circuit, the capacitive reactance is $X_C = 1/(2\pi fC)$. The current is $I_C = V/X_C = 2\pi fCV$. Here, current increases proportionally with frequency.

The analysis shows that increasing AC frequency decreases current in the inductive circuit while increasing current in the capacitive circuit.

Final answer: $\boxed{D}$

Hence, the correct answer is option: 'D'.

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