Alternating Current Concepts

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Questions and Answers

What happens to the period time of a sine wave as rpm increases?

It fluctuates

It is increased

It remains constant

It is reduced (correct)

How many cycles does a four-pole generator complete per revolution?

Four

Three

One

Two (correct)

When does the peak value of a sine wave occur?

At the end of the cycle

Twice each cycle (correct)

Constantly throughout the cycle

At the start of the cycle

What is the peak-to-peak value of a sine wave?

The magnitude between peak positive and peak negative values Signup and view all the answers

Which of the following best defines instantaneous voltage or current?

The value at any time on the sine wave Signup and view all the answers

How does an increase in poles affect the number of cycles completed in a revolution by a generator?

Increases the number of cycles Signup and view all the answers

In a three-phase AC generator, what is the phase difference between the three conductors?

120° Signup and view all the answers

If two sine waves are out of phase, what does it mean?

They do not reach their maximum and minimum points at the same time Signup and view all the answers

Which of the following is NOT a type of AC signal waveform mentioned in the text?

Gaussian wave Signup and view all the answers

What is a distinguishing feature of alternating waves, according to the text?

Equal areas are enclosed above and below the time axis Signup and view all the answers

In the context of AC signals, what does the term 'waveform' refer to?

The shape of the signal over time Signup and view all the answers

Which of the following statements about AC voltage levels is true, based on the information in the text?

They alternate between positive and negative values Signup and view all the answers

What determines the direction of current movement in an alternating current (AC) circuit?

The generated terminal voltage polarities Signup and view all the answers

What is the relationship between the amplitude of the positive and negative alternations in an AC waveform?

The amplitude of the positive alternation and the amplitude of the negative alternation are the same Signup and view all the answers

What is the relationship between the current in an AC circuit and the current in a DC circuit?

AC current is a function of time, while DC current is constant Signup and view all the answers

What is the most common waveform used to represent AC?

Sinusoidal wave Signup and view all the answers

What is the relationship between the speed of a conductor cutting through a magnetic field and the induced EMF?

The faster the conductor cuts through the magnetic field, the greater the induced EMF Signup and view all the answers

What is the purpose of a filter in an electrical circuit?

To remove unwanted frequency components from the signal Signup and view all the answers

Study Notes

Sine Waves and AC Power

The period of a sine wave is the time taken for one cycle, and it decreases as the rotational speed (rpm) increases.
The number of poles in a generator affects the number of cycles completed in a revolution (e.g., two-pole generator completes one cycle per revolution, four-pole generator completes two cycles per revolution).
Peak voltage or current occurs twice in each cycle, at the positive and negative maximum values.
Peak-to-peak voltage or current is the magnitude of the voltage or current between the peak positive and peak negative values.
Instantaneous voltage or current is the value at any time on the sine wave, ranging from zero to peak value.

Phase and Sine Waves

Sine waves can be in-phase or out of phase, depending on whether they reach their maximum and minimum points at the same instant of time.
When sine waves are out of phase, a phase difference exists between them, meaning they do not reach their maximum and minimum points simultaneously.

Three-Phase AC Power

A three-phase (3Ø) generator has three conductors, producing three phases of AC power that are 120° apart.
Three-phase AC power is used in many applications.

AC Signal Types

AC signals include sine waves, square waves, triangular waves, and sawtooth waves, among others.
AC voltage levels change with time, alternating between positive and negative values.
The distinguishing feature of alternating waves is that equal areas are enclosed above and below the time-axis.
The amplitude of the positive and negative alternations are the same.

Simple AC Generator

A simple AC generator consists of a coil rotated through a uniform magnetic field at a constant speed.
The sinusoidal sine wave represents the induced EMF at each instant of time during 360° rotation of the loop.
AC, unlike DC, flows first in one direction and then in the opposite direction.
The current amperage is a function of time, unlike DC amperage which is constant.

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Description

Test your knowledge on concepts related to alternating current, including positive and negative alternations, direction of current movement, voltage terminal polarities, and amplitude calculation.