Q. No.The variation of EMF with time for four types of generators is shown in the figures. Which amongst them can be called AC voltage?
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| (a) | (b) |
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| (c) | (d) |
Choose the correct option from the given ones:
| 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 \(6~\text A.\) When another alternating current passes through the circuit, the AC ammeter reads \(8~\text A.\) Then the reading of this ammeter if DC and AC flow through the circuit simultaneously is:
1. \(10 \sqrt{2}~\text A\)
2. \(14~\text A\)
3. \(10~\text A\)
4. \(15~\text A\)
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. | \(0.4\) | \(-\pi/4\) |
| 2. | \(2.5\) | \(-\pi/2\) |
| 3. | \(2.5\) | \(+\pi/2\) |
| 4. | \(2.5\) | \(-\pi/4\) |
| 1. | AC cannot pass through DC Ammeter. |
| 2. | AC changes direction. |
| 3. | Average value of current for the complete cycle is zero. |
| 4. | DC Ammeter will get damaged. |
A direct current of \(5~ A\) is superimposed on an alternating current \(I=10sin ~\omega t\) 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. | \(15~A\) |
| 1. | about \(14~\text{A}\) | 2. | about \(28~\text{A}\) |
| 3. | about \(20~\text{A}\) | 4. | cannot say |
| 1. | \(60\) Hz and \(240\) V |
| 2. | \(19\) Hz and \(120\) V |
| 3. | \(19\) Hz and \(170\) V |
| 4. | \(754\) Hz and \(70\) V |
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. \( \frac{1}{2}\left(i_1^2+i_2^2\right)^{1 / 2}\)
The peak value of an alternating emf \(E = E_{0}\sin\omega t\) is \(10\) volts and its frequency is \(50\) Hz. At a time \(t=\frac{1}{600}~\text{s},\) the instantaneous value of the emf will be:
| 1. | \(1\) volt | 2. | \(5 \sqrt{3}\) volts |
| 3. | \(5\) volts | 4. | \(10\) volts |
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 \(\frac{\pi}{2}\). |
| 2. | The voltage leads the current by \(\frac{\pi}{2}\). |
| 3. | The voltage and the current are in phase. |
| 4. | The voltage leads the current by \(\pi\). |
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