AC or alternating current is the type of current that reverses its direction many times a second at regular intervals. The most popular type of alternating voltage is the sinusoidal alternating voltage. It can be obtained by rotating a coil with constant angular velocity in a uniform magnetic field. MCQs.net shares top 10 MCQs on the alternating current:

## The time taken to complete one cycle of alternating quantity is known as

The time taken to complete one cycle of alternating quantity is known as:

- Time period
- Frequency
- Amplitude
- Instantaneous value

Correct answer: 1. Time period

Explanation: The time period of AC waveform is defined as the time required to complete one cycle. It is represented using letter T.

## Number of cycles completed in one second is known as

Number of cycles completed in one second is known as:

- Time period
- Frequency
- Amplitude
- Instantaneous value

Correct answer: 2. Frequency

Explanation: Frequency is defined as the number of cycles completed in one second. It is measured in hertz. Where 1 Hertz = 1 cycle/s or 1C/s

## The correct mathematical relationship between angular frequency and frequency is

The correct mathematical relationship between angular frequency and frequency is:

- ω = 2π/f
- ω = 2π+f
- ω = 2/π.f
- ω = 2πf

Correct answer: 4. ω = 2πf

## The correct formula for form factor is

The correct formula for form factor is:

- Form factor = RMS value/Average value
- Form factor = RMS value x Average value
- Form factor = RMS value + Average value
- Form factor = RMS value – Average value

Correct answer: 1. Form factor = RMS value/Average value

Explanation: The form factor of any wave depends on the waveform of alternating quantity. Its least value is 1 and it can be as high as 5 for other waves.

## The form factor for sinusoidal waveform is

The form factor for sinusoidal waveform is:

- 0.55
- 0.73
- 1.11
- 2.52

Correct answer: 3. 1.11

Explanation:

Form factor = RMS value/Average = (0.707 * Max Value / 0.637 * Max value) = 1.11

## The correct formula for peak factor is

The correct formula for peak factor is:

- Peak factor = Max value/RMS value
- Peak factor = Max value x RMS value
- Peak factor = Max value + RMS value
- Peak factor = Max value – RMS value

Correct answer: 1. Peak factor = Max value/RMS value

## The peak factor for sin wave is

The peak factor for sin wave is:

- 0.893
- 1.414
- 1.730
- 2.535

Correct answer: 2. 1.414

Explanation:

Formula for peak factor = Max value / RMS value

= Max value/(0.707 * Max value) = 1.414

## Which of following produces ac voltage

Which of following produces ac voltage:

- Crystal
- Friction
- Photoelectric effect
- None of these

Correct answer: 1. Crystal

Explanation: A piezoelectric transducer comprises that is sandwiched between two metal plates. When sound wave strikes one or bother plates, the vibrate. The crystal picks up the vibration which translates into weak AC voltage.

## Choke in fluorescent tube serves to

Choke in fluorescent tube serves to:

- Increase the current
- Decrease the current
- Increase the voltage momentarily
- Decrease the voltage momentarily

Correct answer: 3. Increase the voltage momentarily

## The AC system is preferred over the DC system for transmission since

The AC system is preferred over the DC system for transmission since:

- AC voltage can be easily changed in magnitude
- High voltage DC transmission is less efficient
- DC motors don’t have good speed control
- All of these

Correct answer: 1. AC voltage can be easily changed in magnitude

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