Question

An alternating current of frequency 'f' is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is, 

(a) R + 2πfL 

(b) √[R² + 4π²f²L²] 

(c) √[R² + L²] 

(d) √[R² + 2πfL]

Answer 1

 The correct option (b) √[R² + 4π²f²L²]

Explanation:

Circuit is R – L series circuit, hence impedance

z = √[R² + ω²L²]

z = √[R² + (2πf)²L²]

z = √[R² + 4π²f²L²]