Question

the power factor of a series L-C-R circuit when at resonance is

• A. zero
• B. 0.5
• C. 1
• D. depends on values of L, C and R

Answer 1

Answer: (C)

1

Answer 2

Average power of circuit is given by $P=E_{ rms } \times i_{ rms } \times \cos \phi$ In a series LCR circuit at resonance voltage and current being in same phase, therefore $\phi=0$. Hence, power factor $=\cos \phi=\cos 0^{\circ}=1$