Question

The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity w is,

(a) (R/ωL) 

(b) [R/{R² + ω²L²}^(1/2)]

(c) (ωL/R) 

(d) [R/{R² – ω²L²}^(1/2)]

Answer 1

The correct option (b) [R/{R² + ω²L²}^(1/2)]

Explanation:

cos ɸ (R/Z)

Where Z = √[R² + XL²] -------- RL series circuit

Hence cos ɸ = [R/{R² + ω²L²}^(1/2)].