In an LCR circuit, energy dissipates in
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → R only
The average power in an ac circuit is \( P = V_{\mathrm{rms}}I_{\mathrm{rms}}\cos\phi \). In a pure inductor or a pure capacitor the current and voltage differ in phase by \( 90^\circ \), so \( \cos\phi = 0 \) and the average power is zero.
\( P_{L} = P_{C} = V_{\mathrm{rms}}I_{\mathrm{rms}}\cos90^\circ = 0 \)
L and C only store energy for part of each cycle and return it to the source in the next part. Energy is dissipated only in the resistor, as Joule heating:
\( P = I_{\mathrm{rms}}^{2}R \)
NCERT (2026-27):
Summary – “… 7. There are no power losses associated with pure capacitances and pure inductances in an ac circuit. The only element that dissipates energy in an ac circuit is the resistive element.”