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%
From NCERT
NEET - 2019
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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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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%
From NCERT
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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:  AC vs DC |
 60%
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%
From NCERT
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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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The time required for a 50 Hz sinusoidal alternating current to change its value from zero to the r.m.s. value will be:

1. 1.5×10-2 s

2. 2.5×10-3 s

3. 10-1 s

4. 10-6 s

Subtopic:  RMS & Average Values |
 76%
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The r.m.s. value of the potential difference V shown in the figure is:

1. V0/3

2. V0

3. V0/2

4. V0/2

Subtopic:  RMS & Average Values |
 74%
From NCERT
AIPMT - 2011
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The output current versus time curve of a rectifier is shown in the figure. The average value of the output current in this case will be:

1. 0 2. \(I_0 \over 2\)
3. \(2I_0 \over \pi\) 4. \(I_0\)
Subtopic:  RMS & Average Values |
 66%
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