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. | \(0.4\) | \(-\pi/4\) |
2. | \(2.5\) | \(-\pi/2\) |
3. | \(2.5\) | \(+\pi/2\) |
4. | \(2.5\) | \(-\pi/4\) |
Alternating current cannot be measured by a D.C. ammeter because:
1. | A.C. cannot pass through D.C. Ammeter |
2. | A. C. changes direction |
3. | Average value of current for the complete cycle is zero |
4. | D.C. 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. | \(15~A\) |
In a heating arrangement, an alternating current having a peak value of \(28~\mathrm{A}\) 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. | \(14~\mathrm{A}\) | about2. | \(28~\mathrm{A}\) | about
3. | \(20~\mathrm{A}\) | about4. | cannot say |