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 |
78%
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NEET - 2019
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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 |
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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:  AC vs DC |
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Alternating current cannot be measured by a DC ammeter because:
 1 AC cannot pass through DC Ammeter. 2 AC changes direction. 3 Average value of current for the complete cycle is zero. 4 DC Ammeter will get damaged.
Subtopic:  AC vs DC |
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In a heating arrangement, an alternating current having a peak value of $$28~\text{A}$$ 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 $$14~\text{A}$$ 2 about $$28~\text{A}$$ 3 about $$20~\text{A}$$ 4 cannot say
Subtopic:  AC vs DC |
56%
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A generator produces a voltage that is given by $$V = 240\sin(120t)$$, where $$t$$ is in seconds. The frequency and rms 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 |
83%
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An alternating current is given as $$i = i_1\cos\omega t- i_2 \sin \omega t.$$ 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 |
80%
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The peak value of an alternating emf $$E = E_{0}\sin\omega t$$ is $$10$$ volts and its frequency is $$50$$ Hz. At a time $$t=\frac{1}{600}~\text{s},$$ the instantaneous value of the emf will be:

 1 $$1$$ volt 2 $$5 \sqrt{3}$$ volts 3 $$5$$ volts 4 $$10$$ volts
Subtopic:  RMS & Average Values |
77%
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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 $$\frac{\pi}{2}$$. 2 The voltage leads the current by $$\frac{\pi}{2}$$. 3 The voltage and the current are in phase. 4 The voltage leads the current by $$\pi$$.
Subtopic:  RMS & Average Values |
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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 |
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