Free Phase of Alternating Current MCQs with Answers
29 Phase of Alternating Current MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Phase describes the position of an alternating voltage or current within its cycle and the phase difference between two sinusoidal quantities. The topic covers in phase signals, phase angle and lead or lag in resistive, inductive and capacitive circuits, rather than the amplitude or frequency of the supply.
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- A. equal to its peak value
- B. the peak value divided by the square root of 2
- C. the peak value multiplied by 2
- D. always zero
Explanation: The rms value is about 0.707 of the peak and is defined as the steady direct current that would dissipate the same power in a given…
Correct answer: the peak value divided by the square root of 2- A. 440 V
- B. 220 V
- C. 311 V
- D. 155 V
Explanation: Dividing 311 by the square root of 2, that is by about 1.414, gives roughly 220 V, the standard supply voltage in Pakistan.
Correct answer: 220 V- A. 50 Hz
- B. 60 Hz
- C. 100 Hz
- D. 220 Hz
Explanation: Pakistan, like most of Asia and Europe, uses 50 Hz at 220 V, while North America uses 60 Hz at 110 V.
Correct answer: 50 Hz- A. the current is too large
- B. the deflection reverses every half cycle and the pointer cannot follow, so it averages to zero
- C. the galvanometer has no coil
- D. AC does not flow through a galvanometer
Explanation: The torque reverses with the current, and at 50 Hz the inertia of the pointer prevents it from following, so it simply sits at zero.
Correct answer: the deflection reverses every half cycle and the pointer cannot follow, so it averages to zero- A. 7.07 A
- B. 14.14 A
- C. 10 A
- D. 20 A
Explanation: The peak is the rms multiplied by the square root of 2, so 10 times 1.414 gives 14.14 A.
Correct answer: 14.14 A- A. pi radians
- B. pi/2 radians
- C. 2 pi radians
- D. pi/4 radians
Explanation: A complete cycle is 360 degrees or 2 pi radians, so 90 degrees is a quarter of a cycle, that is pi over 2 radians.
Correct answer: pi/2 radians- A. A digital waveform
- B. An analogue waveform
- C. Discrete waveform
- D. None at all
Explanation: An alternating voltage changes continuously with time and can take a range of values, so it is an analogue waveform.
Correct answer: An analogue waveform- A. I = 2I∫Sin(πt/2)
- B. I = 2I∫Sin(2πt)
- C. I = 2ISinπt
- D. I = I∫sin(2πt)
Explanation: The original current has amplitude I₀ and angular frequency π rad/s, so doubling both gives I = 2I₀ sin(2πt), with amplitude 2I₀ and…
Correct answer: I = 2I∫Sin(2πt)9. To find the r.m.s value of an alternating current mathematically we need to have ________________?
- A. Mean value of I2
- B. Square root of mean value of I2
- C. Square root of I2
- D. Square of 1/2
Explanation: The RMS current is defined as the square root of the mean of the square of the instantaneous current: Irms = √(mean of I²).
Correct answer: Square root of mean value of I2- A. 20A
- B. 20.66A
- C. 6.66A
- D. 5.66A
Explanation: For a sinusoidal current, Ipeak = √2 Irms = 1.414 x 4.0 A = 5.66 A. The frequency of 50 Hz and resistance of 10 Ω are not needed to find…
Correct answer: 5.66A- A. Average current
- B. Sinusoidal current
- C. r.m.s current
- D. Net current
Explanation: Heating in a resistor depends on I²R, so the steady current producing the same average heating as an AC current is its RMS current.
Correct answer: r.m.s current- A. 9V
- B. 18V
- C. 4.5V
- D. 0V
Explanation: Vp-p=2VpSubstituting the values from the question, we get Vp-p = 2(9)Vp-p = 18V
Correct answer: 18V- A. Period
- B. Cycle
- C. Instantaneous value
- D. Sin wave
Explanation: The duration of one cycle is known as the period. The period is the time it takes for a wave to complete one full cycle, which is…
Correct answer: Period- A. 0.5 x 10^-3 sec
- B. 0.5 second
- C. 5 sec
- D. 2 sec
Explanation: Formula: Frequency = 1/t t = 1/2000= 0.5 x 10-3 sec
Correct answer: 0.5 x 10^-3 sec- A. 2A
- B. A/√2
- C. 2√2A
- D. Zero
Explanation: The instantaneous current is given by I = A sin (wt). Here, A represents the peak current Imax.
Correct answer: A/√2- A. V0=1.414 Vrms
- B. V0=10.10Vrms
- C. V0=10.70 Vrms
- D. Both A and B
Explanation: This statement is correct. V0 represents the peak value of an alternating voltage, while Vrms represents the root mean square (RMS) value…
Correct answer: V0=1.414 Vrms- A. 14.1 A
- B. 10 A
- C. 20 A
- D. 28.2 A
Explanation: The root mean square (rms) value of an alternating current (AC) can be calculated from its peak value using the following formula: Irms =…
Correct answer: 14.1 A- A. 100Hz
- B. 25Hz
- C. 50Hz
- D. 75Hz
Explanation: The equation for the alternating voltage you've provided is in the form of Vt=Vm sin(ωt)where:Vm is the peak voltage, andω is the angular…
Correct answer: 25Hz- A. they both become zero.
- B. they both become infinite.
- C. the voltage leads the current.
- D. the current leads the voltage.
Explanation: * The question explicitly states, "the waveform of the current lags behind it [voltage]." This directly means that the voltage is ahead of…
Correct answer: the voltage leads the current.- A. 220 V
- B. 400 V
- C. 440 V
- D. 1100 V
Explanation: In a three-phase alternating current supply, the voltage across any two power lines is typically 400 V.
Correct answer: 400 VPhase of Alternating Current MCQs: common questions
Are these Phase of Alternating Current MCQs free?
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There are 29 Phase of Alternating Current MCQs in the Physics bank, shown 20 to a page with the correct answer and an explanation on each.
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Yes. Each Phase of Alternating Current question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
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