Question

What is wattless current?

Hint:

Wattless current is also called \textbf{reactive current} and contributes to the \textbf{reactive power} in the circuit.

Answer 1

Step 1: In an alternating current (AC) circuit, the total current can be resolved into two distinct components based on its phase relationship with the applied voltage: - The active current (or real component) which is in phase with the voltage. This component is responsible for performing real work, such as producing heat, light, or mechanical energy. - The wattless current (or reactive component), which is out of phase with the voltage by \(90^\circ\). This component does not perform any net work over a full cycle; instead, it simply transfers energy back and forth between the source and the reactive components (inductors and capacitors) of the circuit.
Step 2: The wattless current primarily arises in circuits with purely inductive or purely capacitive loads, where the phase difference between voltage and current is exactly \(90^\circ\). In such cases, the current either leads or lags the voltage by a quarter cycle, resulting in zero average power consumption.
Step 3: The power consumed in an AC circuit is given by the expression: \[ P = VI \cos \phi, \] where \( V \) is the RMS voltage, \( I \) is the RMS current, and \( \phi \) is the phase angle between voltage and current. For wattless current, \( \phi = 90^\circ \), hence: \[ P = VI \cos 90^\circ = VI \times 0 = 0. \] Therefore, the power associated with wattless current is zero, confirming that it does not contribute to any real energy transfer in the circuit.