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)

 

1.	(a) and (d)
2.	(a), (b), (c), and (d)
3.	(a) and (b)
4.	only (a)

A circuit when connected to an AC source of \(12~\text{V}\) gives a current of \(0.2~\text{A}\). The same circuit when connected to a DC source of \(12~\text{V}\), gives a current of \(0.4~\text{A}\). The circuit is:

For the circuit shown in the figure, the time constant is

$1.<mspace\; width="1em"></mspace>\frac{10}{11}s$
$2.<mspace\; width="1em"></mspace>\frac{9}{10}s$
$3.<mspace\; width="1em"></mspace>\frac{5}{7}s$
$4.<mspace\; width="1em"></mspace>\frac{3}{4}s$

If i=2t, then the R.M.S. value of current between 0 to 2 second is

$1.<mspace\; width="1em"></mspace>\sqrt{\frac{2}{3}}$
$2.<mspace\; width="1em"></mspace>\frac{4}{\sqrt{3}}$
$3.<mspace\; width="1em"></mspace>\sqrt{\frac{5}{3}}$
$4.<mspace\; width="1em"></mspace>zero<mspace\; width="1em"></mspace>$

L, C, and R denote inductance, capacitance, and resistance respectively. pick out the combination which does not have the dimension of frequency.

$1.<mspace\; width="1em"></mspace>\frac{1}{RC}$
$2.<mspace\; width="1em"></mspace>\frac{R}{L}$
$3.<mspace\; width="1em"></mspace>\frac{1}{\sqrt{Lc}}$
$4.<mspace\; width="1em"></mspace>\frac{C}{L}$

The phase difference ($\varphi$) between emf and current in LCR series a.c. circuit is

$1.<mspace\; width="1em"></mspace>\varphi =<mspace\; width="1em"></mspace>0$
$2.<mspace\; width="1em"></mspace>0\le \varphi <\frac{\mathrm{\pi }}{2}$
$3.\frac{\mathrm{\pi }}{2}<\varphi <\mathrm{\pi }$
$4.<mspace\; width="1em"></mspace>\varphi =\mathrm{\pi }$

The primary and secondary coils of an ideal transformer have 100 and 5000 turns respectively. The magnetic flux linking the primary coil is given by $\varphi$= 20t + 10. The output voltage across the secondary coil is

1. 20 V

2. 500 V

3. 1000 V

4. 10000 V

In the LCR-circuit shown below, if the reading of the voltmeters $V_{1<mspace\; width="1em"></mspace>}$and $V_2$ are same, then

1. ${\omega }^2=\frac{1}{LC}$

2. Reading of the voltmeter V is 50 V

3. Reading of the ammeter A is 5 A

4. All of these

If \(R\) and \(L\) are resistance and inductance of a choke coil and \(f\) is the frequency of current through it, then the average power of the choke coil is proportional to:
1. \(R ~\)
2. \(\frac{1}{f^2}\)
3. \(\frac{1}{L^2}\)
4. All of these

Which of the following is/are copper loss/losses in a transformer?

1. Hysteresis loss

2. Eddy current loss

3. Heat loss in the primary and second coils

4. Both (1) & (2)