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) |
An AC ammeter is used to measure the current in a circuit. When a given direct current passes through the circuit, the ac ammeter reads 6 A. When another alternating current passes through the circuit, the AC ammeter reads 8 A. Then the reading of this ammeter if DC and AC flow through the circuit simultaneously is:
1. $10\sqrt{2}$ A
2. 14 A
3. 10 A
4. 15 A
In the diagram, two sinusoidal voltages of the same frequency are shown. What is the frequency and the phase relationship between the voltages?
Frequency in Hz | Phase lead of N over M in radians | |
1. | 0.4 | –π/4 |
2. | 2.5 | –π/2 |
3. | 2.5 | +π/2 |
4. | 2.5 | –π/4 |
A direct current of 5 A is superimposed on an alternating current I = 10$\mathrm{sin}\omega t$ flowing through a wire. The effective value of the resulting current will be:
1. \(15/2~A\)
2. $5\sqrt{3}A$
3. $5\sqrt{5}A$
4. 15 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 |
The variation of the instantaneous current (I) and the instantaneous emf (E) in a circuit are shown in the figure. Which of the following statements is correct?
1. | The voltage lags behind the current by π/2. |
2. | The voltage leads the current by π/2. |
3. | The voltage and the current are in phase. |
4. | The voltage leads the current by π. |
The time required for a 50 Hz sinusoidal alternating current to change its value from zero to the r.m.s. value will be:
1. $1.5\times {10}^{-2}$ $\mathrm{s}$
2. $2.5\times {10}^{-3}$ $\mathrm{s}$
3. ${10}^{-1}$ $\mathrm{s}$
4. ${10}^{-6}$ $\mathrm{s}$
The r.m.s. value of the potential difference V shown in the figure is:
1. ${\mathrm{V}}_{0}/\sqrt{3}$
2. ${\mathrm{V}}_{0}$
3. ${\mathrm{V}}_{0}/\sqrt{2}$
4. ${\mathrm{V}}_{0}/2$
The output current versus time curve of a rectifier is shown in the figure.
The average value of the output current in this case will be:
1. 0
2. $\frac{{I}_{0}}{2}$
3. $\frac{2{I}_{0}}{\pi}$
4. I_{0}