A coil of inductance in series with a resistor is connected to a (rms)

PHYSICS · Subjective · CBSE · Physics · Alternating Current · Alternating Current

Problem

A coil of inductance

L=0.15\,\text{H}

in series with a resistor

R=40\,\Omega

is connected to a

200\,\text{V}

(rms),

60\,\text{Hz}

ac mains. A capacitor of capacitance

C

is also connected in series. (i) If

C=80\,\mu\text{F}

, calculate the rms current drawn from the supply. (ii) The capacitance is now adjusted so that the current becomes maximum at

60\,\text{Hz}

. Find the new value of

C

required. (iii) Keeping the value of

C

found in part (ii), the supply frequency is suddenly doubled to

120\,\text{Hz}

while the supply voltage remains the same. Calculate the new rms current and explain qualitatively why it differs from the value obtained in part (ii).

Related theory

Resonance in AC Circuits
AC Circuit Analysis
Alternating current
Series LCR circuit
AC applied to a series LCR circuit

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