Question

In a series LCR circuit, obtain the condition under which watt-less current flows in the circuit ?

Answer 1

Average power dissipated through a series LCR circuit is given by \[P_{av} = E_v I_v \cos\left( \phi \right)\]

where, E_v = rms value of alternating voltage
            I_v = rms value of alternating current
            Φ = phase difference between current and voltage
For wattless current, the power dissipated through the circuit should be zero.

\[i . e . , \cos\left( \phi \right) = 0\]

\[ \Rightarrow \phi = \frac{\pi}{2}\]

Hence, the condition for wattless current is that the phase difference between the current and voltage should be π/2 and the circuit is purely inductive or purely capacitive.