In the circuit shown, L = 1 μ H , C = 1 μ F a n d R = 1 k Ω . They are connected in series with an a.c.…

In the circuit shown, L = 1 μH, C=1 μF and R=1 kΩ.  They are connected in series with an a.c. source V=V0 sinωt as shown. Which of the following options is/are correct?

  1. At ω106 radsec-1  the circuit behaves as a capacitor
  2. The frequency at which the current will be in phase with the voltage is independent of R
  3. The current will be in phase with the voltage if ω=104 radsec-1 
  4. At ω~0  the current flowing through the circuit becomes nearly zero

Solution

The current will be in phase with voltage when phase angle is zero, 

tanϕ=ωL-1ωCR=0

Where ω, L, C, R are the angular frequency, inductance, capacitance and resistance respectively.

ω=ω0=1LC

ωοis independent of R

(resonant frequency) ω0=106 rad/s

Current in the circuit is given by,

i0=V0R2+ωL-1ωC2

When ω0, i00

For  ωω0 circuit behaves as inductor.

Asked in: JEE Advanced 2017 (Paper 1)

Practice more AC Circuits questions on Aicharya