In a heating arrangement, an alternating current having a peak value of \(28~\text{A}\) is used. To produce the same heat energy, if direct current is used to produce the same amount of heat, then its magnitude will be:

1.	about \(14~\text{A}\)	2.	about \(28~\text{A}\)
3.	about \(20~\text{A}\)	4.	cannot say

The variation of EMF with time for four types of generators is shown in the figures. Which amongst them can be called AC voltage?

(a)	(b)
(c)	(d)

Choose the correct option from the given ones:

A transformer is used to light a \(100~\text{W}\) and \(110~\text{V}\) lamp from a \(220~\text{V}\) main. If the main current is \(0.5~\text{A},\) the efficiency of the transformer is approximately:
1. \(30\%\)
2. \(50\%\)
3. \(90\%\)
4. \(10\%\)

In an electrical circuit \(R,\) \(L,\) \(C\) and an AC voltage source are all connected in series. When \(L\) is removed from the circuit, the phase difference between the voltage and the current in the circuit is \(\tan^{-1}\sqrt{3}\). If instead, \(C\) is removed from the circuit, the phase difference is again \(\tan^{-1}\sqrt{3}\). The power factor of the circuit is:

For a series \(\mathrm{LCR}\) circuit, the power loss at resonance is:
1. \(\frac{V^2}{\left[\omega L-\frac{1}{\omega C}\right]}\)

2. \( \mathrm{I}^2 \mathrm{~L} \omega \)

3. \(I^2 R\)

4. \( \frac{\mathrm{V}^2}{\mathrm{C} \omega} \)

An inductor of \(20~\text{mH}\), a capacitor of \(100~\mu \text{F}\), and a resistor of \(50~\Omega\) are connected in series across a source of emf, \(V=10 \sin (314 t)\). What is the power loss in this circuit?
1. \( 0.79 ~\text{W} \)
2. \( 0.43 ~\text{W} \)
3. \( 2.74 ~\text{W} \)
4. \( 1.13 ~\text{W}\)

A light bulb is rated at \(100~\text{W}\) for a \(220~\text{V}\) AC supply. The RMS current through the bulb is:
1. \(0.243\) A
2. \(0.454\) A
3. \(0.222\) A
4. \(0.312\) A

A \(15.0~{\mu \text F}\) capacitor is connected to a \(220~\text {V},\) \(50~\text {Hz}\) source. If the frequency is doubled, what happens to the capacitive reactance and the current?