An alternating current is given as i = i₁ cos ωt - i₂ sin ωt. The value of rms current is given by:

1.  $\frac{{\mathrm{i}}_1 + {\mathrm{i}}_2}{\sqrt{2}}$

2.  $\frac{\left|{\mathrm{i}}_1 + {\mathrm{i}}_2\right|}{\sqrt{2}}$

3.  $\sqrt{\frac{{\mathrm{i}}_1^2 + {\mathrm{i}}_2^2}{2}}$

4.  $\sqrt{\frac{{\mathrm{i}}_1^2 + {\mathrm{i}}_2^2}{\sqrt{2}}}$

In a step-up transformer, the turn ratio is 1:2 . A Leclanche cell (e.m.f. 1.5 V) is connected across the primary coil. What would be the voltage developed in the secondary coil?

1. 3.0 V

2. 0.75 V

3. 1.5 V

4. Zero

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

When a step-down transformer is connected to a 2400 volt line, the output load receives 80 amps of current. The ratio of the turns in the primary and secondary coils is 20:1. If transformer efficiency is 100%, then the current flowing in the primary coil will be:
1. 1600 A
2. 20 A
3. 4 A
4. 1.5 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:

1. 60 Hz and 240 V

2. 19 Hz and 120 V

3. 19 Hz and 170 V

4. 754 Hz and 70 V

In an ac circuit, the current is given by $i=5\sin \left(100t-\frac{{\displaystyle \pi }}{{\displaystyle 2}}\right)$ 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

A circuit consists of 3 ohms of resistance and 4 ohms of 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

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

1. 30°

2. 45°

3. 60°

4. 90°