An alternating current is given as i = i₁ cos \(\omega t\) - i₂ sin \(\omega t\). The value of rms current is given by:
1. \( \frac{1}{\sqrt{2}}\left(i_1+i_2\right) \)
2. \( \frac{1}{\sqrt{2}}\left(i_i+i_2\right)^2 \)
3. \( \frac{1}{\sqrt{2}}\left(i_1^2+i_2^2\right)^{1 / 2} \)
4. \( \frac{1}{2}\left(i_1^2+i_2^2\right)^{1 / 2}\)

A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohms in series. How much current flows across the circuit?

1.  10 A

2.  5 A

3.  33.3 A

4.  3.33 A

A generator produces a voltage that is given by V = 240 sin 120 t, where t is in seconds. The frequency and r.m.s. voltage are:

In an ac circuit, the current is given by \(i=5\sin(100t-\frac{\pi}{2})\) and the ac potential is V = 200 sin(100t) volt. The power consumption is:

1. 20 W

2. 40 W

3. 1000 W

4. 0 

In an LCR circuit having L = 8.0 henry, C = 0.5 μF and R = 100 ohm in series, what is the resonance frequency?

1. 600 radian/sec

2. 600 Hz

3. 500 radian/sec

4. 500 Hz

An ac source of variable frequency f is connected to an LCR series circuit. Which of the following graphs represents the variation of the current I in the circuit with frequency f?

1.		2.
3.		4.

A step–down transformer transforms a supply line voltage of 2200 volt into 220 volt. The primary coil has 5000 turns. The efficiency and power transmitted by the transformer are 90% and 8 kilowatts respectively. How many turns are there in the secondary one?

The power factor of the given circuit is:
           

It is found that the current through the LCR series circuit is at its maximum. If $V_r,V_c\mathrm{ a}nd{\mathrm{ V}}_L$ are potential differences across resistance, capacitor, and inductor respectively, then which of the following is correct?

In a box Z of unknown elements (L or R or any other combination), an ac voltage $E=E_0\sin (\omega t+\varphi )$ $$is applied and the current in the circuit is found to be $I=I_0\sin (\omega t+\varphi +\frac{\pi }{4})$. The unknown elements in the box could be: