Q. In an electrical circuit R, L, C and an a.c. voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π/3. If instead, C is removed from the circuit, the phase difference is again π/3. The power factor of the circuit is
A) √3/2
B) 1/2
C) 1/√2
D) 1
Explanation
[Solution from source] Removing L: tan(π/3) = X_C/R; removing C: tan(π/3) = X_L/R. So X_L = X_C = √3R and with all three present the circuit is at resonance: Z = R, power factor cos φ = 1. 1/2 is the power factor of each reduced circuit, not of the full RLC circuit. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.