Alternating Current

In a series LCR circuit, a resistor of 300 , a capacitor of 25 nF and an inductor of 100 mH are used. For maximum current in the circuit, the angular frequency of the ac source is 104 radians s-1

A series LCR circuit is connected to an alternating source of emf E. The current amplitude at resonant frequency is I0. If the value of resistance R becomes twice of its initial value then amplitude of current at resonance will be

1. I02
2. I0 2
3. 2I0
4. I0

A bulb and a capacitor are connected in series across an ac supply. A dielectric is then placed between the plates of the capacitor. The glow of the bulb :

1. becomes zero
2. remains same
3. increases
4. decreases

When a coil is connected across a 20 V dc supply, it draws a current of 5 A. When it is connected across 20 V, 50 Hz ac supply, it draws a current of 4 A. The self inductance of the coil is mH. (Take = 3)

A capacitor of reactance 4 3 and a resistor of resistance 4 are connected in series with an ac source of peak value 8 2 V. The power dissipation in the circuit is W.

A LCR circuit is at resonance for a capacitor C, inductance L and resistance R. Now the value of resistance is halved keeping all other parameters same. The current amplitude at resonance will be now:

1. halved
2. same
3. Zero
4. double

A coil of negligible resistance is connected in series with 90 resistor across 120 V, 60 Hz supply. A voltmeter reads 36 V across resistance. Inductance of the coil is :

1. 0.91 H
2. 0.76 H
3. 2.86 H
4. 0.286 H

An alternating emf E = 110 2 100t volt is applied to a capacitor of 2 , the rms value of current in the circuit is mA.

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

1. Statement I is true but Statement II is false
2. Statement I is false but Statement II is true
3. Both Statement I and Statement II are true
4. Both Statement I and Statement II are false

When a dc voltage of 100 V is applied to an inductor, a dc current of 5 A flows through it. When an ac voltage of 200 V peak value is connected to inductor, its inductive reactance is found to be 20 3 . The power dissipated in the circuit is W.