Alternating Currents

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 form in which electric power is delivered to businesses and residences, and it is the type of current used in most electric power transmission and distribution systems.

5 Must Know Facts For Your Next Test

1. Alternating current is the standard for power transmission and distribution because it can be easily transformed to higher or lower voltages using a transformer.
2. The direction of the flow of electric charge in an AC circuit periodically reverses, unlike in a DC circuit where the flow is unidirectional.
3. The frequency of an AC signal determines the number of complete cycles per second and is measured in Hertz (Hz).
4. Alternating current is better suited for long-distance power transmission compared to direct current because it can be easily transformed to higher voltages, reducing power losses.
5. The sinusoidal waveform is the most common form of alternating current, where the voltage and current vary sinusoidally with time.

Review Questions

• Explain the key differences between alternating current (AC) and direct current (DC) and why AC is the preferred method for power transmission.
  • The primary difference between AC and DC is the direction of the flow of electric charge. In a DC circuit, the charge flows in a constant, unidirectional manner, while in an AC circuit, the direction of the charge flow periodically reverses. AC is the preferred method for power transmission because it can be easily transformed to higher or lower voltages using a transformer, which allows for more efficient long-distance power transmission with lower power losses. Additionally, AC is the standard form of electricity supplied to homes and businesses, as it can be used to power a wide variety of electrical devices and appliances.
• Describe the role of frequency in alternating current and how it affects the behavior of electrical components and circuits.
  • The frequency of an AC signal, measured in Hertz (Hz), determines the number of complete cycles per second. This frequency plays a crucial role in the behavior of electrical components and circuits. For example, the impedance of capacitors and inductors is frequency-dependent, with capacitors exhibiting lower impedance at higher frequencies and inductors exhibiting higher impedance at higher frequencies. This frequency-dependent behavior allows for the design of various AC circuits, such as filters and tuned circuits, that rely on the frequency-dependent properties of components to achieve desired functionality. Understanding the role of frequency is essential in the analysis and design of alternating current systems, particularly in the context of plane electromagnetic waves.
• Analyze the advantages of using alternating current (AC) over direct current (DC) for power transmission and distribution, and explain how the use of transformers enables these advantages.
  • The primary advantage of using alternating current (AC) over direct current (DC) for power transmission and distribution is the ability to easily transform the voltage levels using a transformer. Transformers allow for the efficient transmission of power over long distances by stepping up the voltage to reduce current and minimize power losses. This is not possible with direct current, as transformers rely on the changing magnetic fields induced by the alternating current to operate. Additionally, the ability to transform voltages allows for the use of higher transmission voltages, further reducing power losses. The use of transformers also enables the distribution of power at different voltage levels to meet the requirements of various electrical loads, from high-voltage transmission lines to low-voltage household circuits. This flexibility and efficiency provided by AC power transmission and the use of transformers are key factors in the widespread adoption of alternating current for electrical power systems.

Related terms

Direct Current (DC): Direct current (DC) is the unidirectional flow of electric charge. In direct current, the flow of charge is constant and in a single direction.

Frequency: Frequency is the number of complete cycles or periods of a periodic phenomenon occurring per unit of time, usually measured in Hertz (Hz).

Transformer: A transformer is a static device that transfers electrical energy from one electrical circuit to another through electromagnetic induction, allowing the voltage to be changed.