What is Alternating Current (AC) and How it works

AC, or Alternating current, is a type of electrical current in which the direction of the flow of electrons periodically reverses. In other words, the voltage or electrical potential difference oscillates in direction and magnitude. This is in contrast to DC, or direct current, in which the electrons flow in only one direction.

AC is the form of electricity that is commonly used to power homes and businesses. It is generated by power plants, usually through the use of generators that convert mechanical energy into electrical energy. Mechanical energy can come from a variety of sources, such as burning fossil fuels, nuclear reactions, or harnessing the energy of moving water or wind.

The most common form of AC power has a frequency of 60 Hz in North America and 50 Hz in most other countries. This means that the current oscillates at a rate of 60 or 50 cycles per second. The voltage also oscillates, with the most common form being a sine wave.

Construction of AC current


AC current is generated by an generator, also known as an alternator. The basic construction of an alternator consists of a rotating rotor and a stationary stator.

The rotor is the moving part of the generator and is typically constructed from a shaft with a series of magnets mounted on it. The shaft is connected to a prime mover, such as a steam turbine or internal combustion engine, which provides the mechanical energy needed to rotate the rotor.

The stator is the stationary part of the generator and is typically constructed from a series of coils of wire. The stator surrounds the rotor with an air gap in between. The coils of wire in the stator are connected to an external circuit, and it’s the stator that generates the AC voltage.

As the rotor rotates within the stator, the rotating magnetic field generated by the magnets on the rotor passes over the coils of wire in the stator. This causes an electrical current to be induced in the coils of wire, which is the AC current. The magnitude and direction of the current in the coils of wire changes as the rotor rotates, resulting in an alternating current.

Wave Form of AC current

The waveform of an AC current is typically a sine wave, a smooth, oscillating wave that varies between a positive and negative value. The sine wave oscillates at a specific frequency, which is the number of oscillations or cycles that occur in one second.


Working of AC current

AC current works by the process of electromagnetic induction. Electromagnetic induction is the phenomenon in which an electrical current is generated in a conductor as it moves through a magnetic field. The changing magnetic field of the rotor in an AC generator induces a current in the stator’s coils, which is then sent out to the external circuit, which is the AC current.

Application of AC current

  • Power generation and transmission
  • Household and Commercial power
  • Electric motors and generators
  • Electronics and Communication
  • Industrial and Medical applications

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