Alternating Current (AC)

Definition

Alternating current (AC) is a type of electrical current where the flow of electric charge periodically reverses direction. This is in contrast to direct current (DC), where the flow is constant and unidirectional. AC is the standard form of electricity used in homes and businesses, allowing for efficient energy transmission over long distances and enabling the use of transformers to change voltage levels.

5 Must Know Facts For Your Next Test

1. AC typically has a sinusoidal waveform, which means that its voltage and current vary smoothly over time.
2. The frequency of AC, measured in hertz (Hz), indicates how many times the current changes direction per second; in North America, this is usually 60 Hz.
3. Transformers play a crucial role in the distribution of AC by stepping up or stepping down voltage levels for efficient transmission.
4. Most household appliances are designed to operate on AC because it is easier to convert to different voltages as needed.
5. The discovery and development of AC systems were significantly advanced by inventors like Nikola Tesla and George Westinghouse in the late 19th century.

Review Questions

• Compare and contrast alternating current (AC) with direct current (DC) in terms of their characteristics and applications.
  • Alternating current (AC) differs from direct current (DC) primarily in how the electric charge flows. AC reverses direction periodically, typically following a sinusoidal waveform, while DC flows steadily in one direction. This characteristic allows AC to be transmitted efficiently over long distances using transformers, making it suitable for powering homes and businesses. DC, on the other hand, is often used in battery-powered devices where a stable voltage is needed.
• Discuss the significance of frequency in alternating current and its impact on electrical systems.
  • Frequency is a critical factor in alternating current systems as it determines how quickly the current changes direction. For example, in North America, AC operates at 60 Hz, meaning it alternates direction 60 times per second. This frequency affects how electrical devices are designed and operated; appliances must be compatible with the frequency of the AC supply to function efficiently. Additionally, variations in frequency can impact power quality and can lead to inefficiencies or damage to sensitive equipment.
• Evaluate the role of alternating current in modern electrical systems and its advantages over other forms of current.
  • Alternating current plays a vital role in modern electrical systems due to its ability to be transmitted over long distances with minimal energy loss. This advantage stems from its compatibility with transformers that can step up voltages for transmission and step them down for safe use in homes. The widespread adoption of AC allows for a standardized grid system that supports various applications, from industrial machinery to household appliances. The flexibility and efficiency of AC make it essential for meeting contemporary energy demands.

Related terms

Direct Current (DC): A type of electrical current where the flow of electric charge is constant and flows in a single direction.

Voltage:

The electric potential difference between two points, which drives the flow of current in a circuit.

Transformer: An electrical device used to change the voltage level of alternating current, enabling efficient transmission over long distances.