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)

Subtopic: Â AC vs DC |
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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

Subtopic: Â AC vs DC |
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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. $$2.5$$ $$-\pi/4$$
Subtopic: Â AC vs DC |
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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
Subtopic: Â AC vs DC |
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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 $$15~A$$
Subtopic: Â AC vs DC |
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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 about $$14~\mathrm{A}$$ 2 about $$28~\mathrm{A}$$ 3 about $$20~\mathrm{A}$$ 4 cannot say
Subtopic: Â AC vs DC |
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