A resistance of $20~ \Omega$ is connected to a source of an alternating potential, $V=220\sin(100 \pi t).$ The time taken by the current to change from its peak value to its rms value will be: 

1.	$0.2~\text{sec}$	2.	$0.25~\text{sec}$
3.	$25 \times10^{-3}~\text{sec}$	4.	$2.5 \times10^{-3}~\text{sec}$

Voltage and current in an ac circuit are given by $V=5\sin \left(100\pi t-\frac{{\displaystyle \pi }}{{\displaystyle 6}}\right)$ and $I=4\sin \left(100\pi t+\frac{{\displaystyle \pi }}{{\displaystyle 6}}\right)$ 

1. Voltage leads the current by 30°

2. Current leads the voltage by 30°

3. Current leads the voltage by 60°

4. Voltage leads the current by 60°

A resistance of $300~\Omega$ 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:

In a region of uniform magnetic induction B = 10^–2 tesla, a circular coil of radius 30 cm and resistance π² ohm is rotated about an axis that is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is :

1. 4π² mA

2. 30 mA

3. 6 mA

4. 200 mA

The impedance of a circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is :

1. 0.4

2. 0.6

3. 0.8

4. 1.0

The power factor of a good choke coil is:

1. Nearly zero

2. Exactly zero

3. Nearly one

4. Exactly one

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