Alternating Current · Question 2

A series LCR circuit with R=20 , L=1.6 H and C=40 F is connected to a variable frequency a.c. source. The inductive reactance at resonant frequency is .

An inductor of 10 mH, capacitor of 0.1 μF and a resistor of 100 Ω are connected in series across an a.c. power supply 220 V, 70 Hz. The power factor of the given circuit is 0.5. The difference in the inductive reactance and capacitive reactance is 3 Ω. The value of is .

The figure given below shows an LCR series circuit with two switches S1 and S2. When switch S1 is closed keeping S2 open, the phase difference ( ) between the current and source voltage is 30° and phase difference is 60° when S2 is closed keeping S1 open. The value of (3L1-L2) is H. [figure]

1. 92
2. 29
3. 13
4. 3

The electric current in the circuit is given as i = io(t/T). The r.m.s current for the period t = 0 to t = T is .

1. io 2
2. io 3
3. io
4. io 6

An inductor stores 16 J of magnetic field energy and dissipates 32 W of thermal energy due to its resistance when an a.c. current of 2 A (rms) and frequency 50 Hz flows through it. The ratio of inductive reactance to its resistance is . ( = 3.14)

For the series LCR circuit connected with 220 V, 50 Hz a.c. source as shown in the figure, the power factor is 10. The value of is . [figure]

1. 4
2. 8
3. 6
4. 10

Using a variable frequency a.c. voltage source the maximum current measured in the given LCR circuit is 50 mA for V = 5 (100t). The values of L and R are shown in the figure. The capacitance of the capacitor (C) used is . [figure]

A capacitor C is first charged fully with potential difference of V0 and disconnected from the battery. The charged capacitor is connected across an inductor having inductance L. In t s, 25% of the initial energy in the capacitor is transferred to the inductor. The value of t is s.

1. LC3
2. LC2
3. LC2
4. LC6

An ac current is represented as i = 5 2 + 10 (650 t + 6 ) Amp The r.m.s. value of the current is

1. 10 Amp
2. 5 2 Amp
3. 100 Amp
4. 50 Amp

For ac circuit shown in figure, R = 100 k and C = 100 pF and the phase difference between Vin and (VB - VA) is 90 . The input signal frequency is 10x rad/sec, where 'x' is . [figure]