Question

Among various circuits constructed with resistor $R$, inductor $L$ and capacitor $C$, the circuit that gives maximum power dissipation is

• A. purely inductive circuit
• B. purely capacitive circuit
• C. purely resistive circuit
• D. $L-C$ series circuit
• E. $C-R$ series circuit

Answer 1

Answer: (C)

Average power dissipated in an AC circuit is given as
$P_{av}=V_{rms}{i}_{rms}\cos \phi$
where, $V_{rms}$ and $i_{rms}$ are the rms value of voltage and current respectively and $\cos \phi$ is the power factor.
The circuit gives maximum power dissipation, i.e. the voltage and current are in same phase, so phase difference is zero, or power factor is maximum, which occurs only in resistive circuit.
So, the circuit that gives maximum power dissipation is purely resistive circuit.