Alternating Current

Definition

Alternating current (AC) is an electric current that periodically reverses direction, in contrast to direct current (DC) which flows in a constant direction. AC is the standard for most household and industrial applications due to its ability to be easily transformed to different voltages and its efficient transmission over long distances.

5 Must Know Facts For Your Next Test

1. Alternating current (AC) is the standard for most household and industrial applications because it can be easily transformed to different voltages, allowing for efficient transmission over long distances.
2. In AC circuits, the direction of the electric charge periodically reverses, unlike in direct current (DC) circuits where the charge flows in a constant direction.
3. The frequency of an AC waveform, measured in Hertz (Hz), determines the number of complete cycles that occur per second, and this frequency can be adjusted using transformers.
4. Alternating current (AC) is generated by rotating generators, where the rotation of a coil of wire in a magnetic field induces an alternating voltage.
5. The ability to easily transform AC voltage levels using transformers is a key advantage of AC over DC, as it allows for efficient long-distance power transmission and distribution.

Review Questions

• Explain how the periodic reversal of direction in alternating current (AC) differs from the constant flow of direct current (DC).
  • In an alternating current (AC) circuit, the direction of the electric charge periodically reverses, flowing first in one direction and then the other. This is in contrast to a direct current (DC) circuit, where the electric charge flows in a constant, unidirectional manner. The periodic reversal of direction in AC is a key characteristic that allows for the efficient transformation of voltage levels using transformers, as well as the effective transmission of power over long distances.
• Describe the role of frequency in the generation and application of alternating current (AC).
  • The frequency of an alternating current (AC) waveform, measured in Hertz (Hz), determines the number of complete cycles that occur per second. This frequency is a crucial parameter in the generation and application of AC. Rotating generators produce AC by inducing an alternating voltage in a coil of wire as it rotates within a magnetic field, and the frequency of the resulting AC is determined by the rotational speed of the generator. Additionally, the frequency of AC can be adjusted using transformers, allowing for efficient power transmission and distribution at different voltage levels.
• Analyze the advantages of alternating current (AC) over direct current (DC) in the context of Ohm's law and electrical power transmission.
  • Alternating current (AC) has several advantages over direct current (DC) in the context of Ohm's law and electrical power transmission. Firstly, the ability to easily transform AC voltage levels using transformers allows for efficient long-distance power transmission, as higher voltages can be used to minimize power losses due to resistance (as described by Ohm's law). Additionally, the periodic reversal of direction in AC means that the net flow of charge over time is zero, which simplifies the application of Ohm's law and allows for the use of simpler circuit analysis techniques. These advantages of AC, combined with its widespread availability and the ease of generating it using rotating machinery, make it the preferred choice for most household and industrial electrical applications.

Related terms

Direct Current (DC): Direct current (DC) is the flow of electric charge that always maintains the same direction, unlike alternating current (AC) which reverses direction periodically.

Transformer: A transformer is a device that converts alternating current (AC) from one voltage level to another, allowing for efficient transmission and use of electrical power.

Frequency: Frequency is the number of complete cycles of an alternating current (AC) waveform that occur in a given time period, typically measured in Hertz (Hz).