For a series LCR circuit the power loss at resonance is : -

In a series LCR (inductor, capacitor, resistor) circuit, power loss at resonance can be calculated using the formula:

$P_{\text{loss}} = I_{\text{rms}}^2 \times R$

Where:

- $P_{\text{loss}}$ is the power loss at resonance,

- $I_{\text{rms}}$ is the RMS current in the circuit, and

- $R$ is the resistance in the circuit.

At resonance, the impedance of the inductor ($X_L$) and the capacitor ($X_C$) cancel each other out, leaving only the resistance ($R$) in the circuit.