In an AC-circuit, the power or rate of energy dissipated is
P=VIcosφ where,
φ= phase difference between voltage and current.
For inductor
(L) and capacitor
(C), the phase difference between
V and
I is
90∘. ∴PL or C=VIcos90∘=0(∵cos90∘=0
For resistor
(R), the phase difference between
V and
I is zero.
∴PR=VIcos0∘=VI(∵cos0∘=1)
Hence, only due to resistor
R, energy is dissipated in an
L−C⋅R circuit.