Electro Magnetic Induction And Alternating Currents Question 141

Question: A telephone wire of length 200 km has a capacitance of 0.014 mF per km. If it carries an ac of frequency 5 kHz, what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum

Options:

A) 0.35 mH

B) 35 mH

C) 3.5 mH

D) Zero

Show Answer

Answer:

Correct Answer: A

Solution:

Capacitance of wire

C=0.014×106×200=2.8×106F=2.8μF

For impedance of the circuit to be minimum XL=XC

Þ 2πνL=12πνC

Þ L=14π2ν2C=14(3.14)2×(5×103)2×2.8×106 =0.35×103H=0.35,mH



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