How does an AC generator function?

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An AC generator or Alternating Current Generator is a device which is used for converting mechanical energy into alternating energy in various appliances. While a DC generator uses direct current, an AC generator uses slip rings to produce alternating current. The AC generator produces AC current in bicycles, electric scooters and microwaves. The steam and gas turbines as well internal combustion engines provide mechanical energy to the AC generators. They are widely used in wind turbines and hydropower plants for converting high-pressure gas streams to lower pressure zones.

Principles, parts, uses and working of an AC generator

An electrical generator helps in transforming mechanical energy into electrical energy. Based on the supply of power, electrical generators are classified into two types, AC and DC.

The electrical current flows only in one direction in a DC generator. On the other hand, the electrical current reverses direction periodically in an AC generator. An AC generator works on Faraday’s law of Electromagnetic induction. The direction of the alternating current can be determined using Fleming’s right-hand rule.


Parts of an AC generator

The parts of an AC generator mainly include yoke, permanent magnets, slip rings, brushes, pole shoe, coils, pole core and armature core. The yoke is the frame which acts as the protecting cover of the generator. All the parts of an AC generator are within the yoke. Magnets help in generating magnetic fields between air gaps. A coil is placed in the magnetic field. The coil is made up of four wires (AB,BC, CD, and DC).


The pole shoe within the pole core houses the windings. This includes the armature windings placed in the armature core. The armature core is produced as a result of the armature flux. The slip rings ensure that the operation is conducted smoothly. The current passes through the brush to which the rings are attached. Twisting of wires are avoided, thanks to the slip rings which pass smoothly through the brushes. 

Working of an AC generator

When a conductor cuts the lines of magnetic flux, EMF is induced, which helps in passing the current through the conductors. A loop generator under the influence of a magnetic field provides a better insight into the mechanism of an AC generator.


We should name the loop placed in the magnetic field as ABCD. Whereas, the loop of wire is named as AB, BC, CD, and DC respectively. The loop is rotated with the help of an external shaft which acts as a primary mover.


The magnetic flux lines move from north pole to south pole, basically from left to right. The loop rotates cutting the magnetic flux, with the help of the shaft.

Fleming’s Right-Hand Rule

If a moving current is placed in a magnetic field, electric current will be induced in it. Fleming’s Right-Hand Rule is used to determine the direction of this induced current. 


If we stretch the thumb, middle finger, and an index finger mutually perpendicular to each other, then the direction of each finger determines the following,


  • Thumb is along the direction of motion of the conductor
  • Middle finger points in the direction of the induced current
  • Index finger signifies the direction of the magnetic field
fleming right hand rule


As the loop rotates, the current inside the wire AB reverses direction. The same happens in the wires BC, CD, and DC, the direction of current changes every half cycle, as the loop rotates.

The slip rings are responsible for movement of wires when the loop is rotated. Current reaches the brushes after passing through the slip rings. Further moving to the load. 


The direction of the current changes for every half-cycle of the loop. A galvanometer is used to note the alternating current at the load end.


Hence an Alternating Current (AC) Generator converts mechanical energy into electrical energy, producing an output of alternating current or voltage.

Read more : The fascinating story behind Hardy-Ramanujan number

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Alternating Current Generator’

The parts of an AC generator mainly include yoke, permanent magnets, slip rings, brushes, pole shoe, coils, pole core and armature core.

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