Question

Power dissipation is maximum in

• A. Pure capacitive circuit
• B. Pure inductive circuit
• C. Pure resistive circuit
• D. None of these

Answer 1

The correct option is C

Pure resistive circuit

The explanation for the correct option:

Option (C): Pure resistive circuit

1. For an AC circuit, Power dissipated is calculated by the formula

$$\begin{gathered} P=V_{rms}{I}_{rms}\cos \varphi \\ {V}_{rms}=RootmeansquareofVoltage \\ {I}_{rms}=RootmeansquareofCurrent \\ \varphi =Phasedifferencebetweencurrentandvoltage \end{gathered}$$

2. In a purely resistive circuit, Current and Voltage are in the same phase therefore phase difference is zero

$$\begin{gathered} \cos \varphi =\cos 0^o \\ \cos \varphi =1 \end{gathered}$$

Therefore power dissipated is maximum

The explanation for incorrect options:

In purely capacitive and inductive circuits, the phase difference is, ${90}^o$and $\cos {90}^o=0$ Therefore power dissipated is equal to zero.

Hence the correct option is (C)