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?
      

Alternating current cannot be measured by a D.C. ammeter because:
1. A.C. can not pass through D.C. Ammeter
2. A. C. changes direction
3. Average value of current for complete cycle is zero
4. D.C. Ammeter will get damaged

A direct current of 5 A is superimposed on an alternating current I = 10$\sin \omega t$ flowing through a wire. The effective value of the resulting current will be:

1. \(15/2~A\)

2. $5\sqrt{\mathrm{3 }}A$

3. $5\sqrt{\mathrm{5 }}A$

4. 15 A

In a heating arrangement, an alternating current having a peak value of 28 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 A

2. about 28 A

3. about 20 A

4. cannot say