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:  AC vs DC |
 79%
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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:  AC vs DC |
 67%
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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. 102 A

2. 14 A

3. 10 A

4. 15 A

Subtopic:  AC vs DC |
 65%
From NCERT
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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:  AC vs DC |
 64%
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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:  AC vs DC |
 57%
From NCERT
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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

Subtopic:  RMS & Average Values |
 84%
From NCERT
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An alternating current is given as i = icos \(\omega t\) - isin \(\omega t\). The value of rms current is given by:
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. \( \frac{1}{2}\left(i_1^2+i_2^2\right)^{1 / 2}\)

Subtopic:  RMS & Average Values |
 81%
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The peak value of an alternating e.m.f. E=E0 sin ωt is 10 volts and its frequency is 50 Hz. At a time \(t=\frac{1}{600}~s,\) the instantaneous value of the e.m.f. will be:

1. 1 volt 2. \(5 \sqrt{3}\) volts
3. 5 volts 4. 10 volts
Subtopic:  RMS & Average Values |
 78%
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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.

Subtopic:  RMS & Average Values |
 79%
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When an alternating voltage is given as \(E = (6 sin\omega t - 2 cos \omega t)\) volt, what is its RMS value?
1. \(4 \sqrt 2 \) V
2. \(2 \sqrt 5\) V
3. \(2 \sqrt 3\) V
4. \(4\) V

Subtopic:  RMS & Average Values |
 77%
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