What is the full form of AC ?


AC and DC are immensely common terms while discussing current and electricity. DC or direct current refers to current that constantly flows in a single direction and thus, has fixed polarity. Direct current can be used to power light bulbs and other such devices without the need for any sort of conversion.

On the other hand, the power supply we receive in our homes comes in the form of alternating current, or AC. This form of current periodically reverses direction and is more economical to transmit over long distances. We will discuss more about AC in this article.

What is Alternating Current?

Formally, we can define alternating current as a form of current that continuously changes its direction at a given frequency. For instance, if we were to attach an ammeter to a circuit wherein AC was flowing, the reading would start from zero, go to a maximum value, then start falling and go to the maximum value in the negative direction. This negative sign simply implies a change in direction. Some ammeters won’t even register AC as the average value would come out to be zero.

Alternating current is the dominant form of electricity transmission across the globe primarily due to its lower transmission cost. However, this form is not suitable for our devices. It needs to be converted to direct current before being utilised, which is why you need an AC adapter in your laptop or mobile chargers, which converts the AC supply into suitable DC format. The current provided by a simple battery is direct current and thus, can be used to power devices directly.

Alternating Current Production

Alternating current is produced via the use of electric generators known as alternators. These alternators convert mechanical motion into electrical energy by a phenomenon known as Faraday’s Law. According to this law, when a loop of wire experiences a changing magnetic field, it develops an electromotive force (EMF) or in other words, a potential difference. AC generators make use of this phenomenon to generate continuously alternating voltage.

Diagram of a simple AC generator

The above diagram shows a very simple AC generator consisting of a pair of magnets and a current loop or coil. When this coil (shown in blue) is rotated, the magnetic field experienced by it changes and thus, an EMF is induced in the circuit.

Note that this diagram also shows how an AC generator can be used to power DC devices like lamps and bulbs using slip rings and graphite brushes. However, for industrial purposes, the magnet is rotated, the coils are kept stationary, and the AC power thus generated is transmitted without conversion to DC.

Application of Alternating Current

The following applications of alternating current are the most common ones

  • AC is the preferred and dominant form of current for commercial electricity transmission. Transmitting AC over long distances is more economical and leads to lesser power losses.

  • Transformers work on the principle of electromagnetic induction, which uses alternating current.

  • Water pumps, drills, electric cars, and various other appliances utilise AC motors, which require AC input.

  • Almost all commercial devices today are designedṣ for AC supply only. For instance, charging a battery is impossible via AC and thus, mobile chargers come with an adapter that converts the supply to DC before it reaches your phone.

Alternating Current Waveform

The AC waveform generally resembles a sine wave, owing to the way that it is produced. The equation that connects the change in magnetic field to the EMF induced in the circuit involves a sine term, which is responsible for the continuous change in direction and magnitude of an AC supply.

The above diagram shows the typical waveform associated with an AC supply. You can see how it is the same as a sine wave graph and continuously varies between a pair of maximum and minimum values with a fixed time period.


AC, or alternating current, is a form of current whose direction is periodically and continuously reversed. It is the preferred format for power transmission from the grid to our homes, owing to lesser power loss and transmission costs. However, AC cannot power our devices directly and thus, must be converted to DC via adapters and rectifiers before being utilised. In graphical terms, alternating current resembles a sine wave when plotted as a function of time.

AC is generated via alternators, which utilise Faraday’s law of electromagnetic induction to produce an alternating voltage in a coil. The coils are placed around a large magnet, which is rotated via a mechanical input like wind turbine or hydropower, leading to the induction of an EMF in the coils. The EMF thus produced is then transmitted to our homes. AC has numerous applications including electric cars, water pumps, drills, transformers, etc.


Q1. What is meant by AC current and AC voltage?

Ans. AC itself is an acronym for alternating current and thus, “AC current” is a redundant term. However, to refer to current or voltage that continuously changes direction, the terms ac current and ac voltage have become immensely common. Thus AC voltage means voltage that continuously reverses direction just as AC current implies current of an alternating nature.

Q2. Out of AC and DC, which one is considered more dangerous?

Ans. Electric current in any form is dangerous and often fatal. However, AC has a more dangerous effect than DC.

Q3. What would happen if we connected our devices to AC without converting it first?

Ans. Depending upon the maximum voltage of the supply, your devices can get damaged and even explode and thus, this is a very bad idea. Some devices like incandescent bulbs may work, though the functionality might not be as expected.

Updated on: 14-Apr-2023


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