Networks Analysis and Synthesis - Engineering

Q1:

An RL series circuit has an impedance of 20 Ω when frequency is 25 Hz. At f= 50 Hz, the impedance will be

A 40 Ω

B 20 Ω

C less than 40 W but more than 20 Ω

D less than 20 W but more than 10 Ω

ANS:C - less than 40 W but more than 20 Ω

Z = R2 + XL2. When frequency is doubled, XL becomes twice but R remains the same.