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An LCR series circuit with 100 \Omega resistance is connected to an AC source of 200 V and angular frequency 300 radians per second. When only the capacitance is removed, the current lags the voltage by 60°. When only the inductance is removed, the current leads the voltage by 60º. Then the current and power dissipated in LCR circuit are respectively

Option: 1

1A, 200 watt


Option: 2

1A, 400 watt


Option: 3

2A, 200 watt


Option: 4

2A, 400 watt


Answers (1)

best_answer

 

R.L Circuit Voltage -

V_{R}= IR

V_{L}= {I}X_{L}

- wherein

 

 

Phase difference -

\tan \phi = \frac{X_{L}}{R}= \tan ^{-1}\left ( \frac{X_{L}}{R} \right )

\phi = \tan ^{-1}\left ( \frac{\omega L}{R} \right )

- wherein

XL  = inductive reactance

R     = resistance

 

 

R C Circuit Voltage -

V_{R}=IR

V_{C}={I}X_{C}

- wherein

 

 

Phase difference -

\tan \phi = \frac{X_{c}}{R}

\phi = \tan ^{-1}\left ( \frac{X_{c}}{R} \right )= \tan ^{-1}\left ( \frac{1}{\omega cR} \right )

-

 

 

At resonance (series resonant and circuit) If X_{L}=X_{c} -

Z_{min}= R

- wherein

Circuit behaves as resistive circuit.

 

 

When capacitance is removed

\tan \theta = \frac{\omega L}{R} or \omega L = 100 \tan 60^{\circ}                             ..................(1)

when inductance is removed

\tan \phi = \frac{1}{(\omega C)(R)} or    =100 \tan 60^{\circ}                       ....................(2)

From equation (1) and (2)   \omega L = \frac{1}{\omega C}

 

So it is a condition of resonance.

            so  z = R = 100 \Omega

            I = v/R = 200/100 = 2A

            Power  P = I2 R = 4 × 100 =  400 W

 

Posted by

manish

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