Alternating current

Alternating current is electric current that periodically reverses direction, usually varying in magnitude over time. It is commonly generated as a repeating waveform and used in power systems.

Sinusoidal waveform: A smooth, periodic waveform whose value follows a sine function. An ideal AC source produces a voltage and current that vary sinusoidally.
Electric power transmission: The transfer of electrical energy from generating stations to consumers over conductors. AC voltage can be stepped up to reduce transmission losses.
Direct current: Electric current that flows in one direction without periodically reversing. Direct current differs from AC in its direction of flow and conversion needs.
Electric current: The rate at which electric charge flows through a surface or circuit. Alternating current is a time-varying form of electric current.
Alternating voltage: Voltage that periodically reverses polarity and typically varies in magnitude. Changing polarity drives current to reverse direction in an AC circuit.
Electrical grid: An interconnected system that generates, transmits, and distributes electrical power. Alternating current is the dominant form used in many national grids.
High-voltage direct current: A method of transmitting electrical power using high-voltage direct current. HVDC can outperform AC on very long or underwater transmission links.
Electrical impedance: The frequency-dependent opposition a circuit presents to alternating current. Impedance generalizes resistance to AC circuits with capacitors and inductors.
Electromagnetic induction: The production of electromotive force by a changing magnetic flux. Generators use changing magnetic flux to induce alternating voltage.
Three-phase electric power: An AC power system using three voltages offset in phase by 120 degrees. Three-phase AC delivers steady power and drives many industrial motors.

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