A resistance of \(20~ \mathrm{ohms}\) is connected to a source of an alternating potential, \(V=220sin(100 \pi t).\) The time taken by the current to change from its peak value to its r.m.s value will be: 

1.	\( 0.2~ \mathrm{sec}\)	2.	\( 0.25~ \mathrm{sec}\)
3.	\(25 \times10^{-3}~ \mathrm{sec}\)	4.	\(2.5 \times10^{-3}~ \mathrm{sec}\)

A resistance of 300 Ω and an inductance of $\frac{1}{\pi }$ henry are connected in series to an ac voltage of 20 volts and a 200 Hz frequency. The phase angle between the voltage and current will be:

1. ${\tan }^{-1}\frac{4}{3}$

2. ${\tan }^{-1}\frac{3}{4}$

3. ${\tan }^{-1}\frac{3}{2}$

4. ${\tan }^{-1}\frac{2}{5}$

In a LCR circuit having L = 8.0 henry, C = 0.5 μF and R = 100 ohm in series. The resonance frequency in radian per second is 

(1) 600 radian/second

(2) 600 Hz

(3) 500 radian/second

(4) 500 Hz

The phase difference between the current and voltage of LCR circuit in series combination at resonance is 

(1) 0

(2) π/2

(3) π

(4) –π

In a series LCR circuit, resistance R = 10Ω and the impedance Z = 20Ω. The phase difference between the current and the voltage is 

(1) 30°

(2) 45°

(3) 60°

(4) 90°

In an ac circuit the reactance of a coil is \(\sqrt{3}\) times its resistance, the phase difference between the voltage across the coil to the current through the coil will be:
1. \( \pi / 3 \)
2. \( \pi / 2 \)
3. \( \pi / 4 \)
4. \( \pi / 6\)

The capacity of a pure capacitor is 1 farad. In dc circuits, its effective resistance will be 

(1) Zero

(2) Infinite

(3) 1 ohm

(4) 1/2 ohm

In an LCR circuit, the potential difference between the terminals of the inductance is 60 V, between the terminals of the capacitor is 30 V and that between the terminals of the resistance is 40 V. The supply voltage will be equal to:

1. 50 V

2. 70 V

3. 130 V

4. 10 V

In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An e.m.f. $E=E_0\cos \left(\omega t\right)$ applied to the circuit. The power consumed in the circuit is:

(1) $\frac{E_0^2}{R}$

(2) $\frac{E_0^2}{2R}$

(3) $\frac{E_0^2}{4R}$

(4) $\frac{E_0^2}{8R}$

In the circuit given below, what will be the reading of the voltmeter 

(1) 300 V

(2) 900 V

(3) 200 V

(4) 400 V