Electric generator

These notes are based on the chapter Magnetic Effect of Electric current class 10 science NCERT book and CBSE syllabus.

Electric generator is a device which converts kinetic energy into electric energy.

Battery is useful for generating power on a small scale. But whenever power generation is required on large scale, electric generator is the preferred device. In all the power plants, electric generator is used for producing electricity. Energy of flow of water or steam is utilized to move the turbine in order to generate electricity.

In hydel power plant, flow of water is the source of kinetic energy to run the turbine. In thermal power plant and nuclear power plant, heat is utilised to convert water into steam. The steam is then utilised to turn the turbine. In a windmill, kinetic energy of wind is utilised to turn the rotor of a windmill. The rotor of the windmill turns the turbine to generate electricity.

In diesel generator, diesel is used as fuel to turn the turbine. The turbine converts mechanical energy into electrical energy.

Principle of Electric Motor

In case of an electric generator a rectangular armature is placed within the magnetic field of a permanent magnet. The armature is attached to wire and is positioned in way that it can move around an axle.

Structure of Electric Generator

The structure of electric generator is similar to that of an electric motor. This means that electric generator contains a rotor shaft inside a magnetic field. The movement of rotor inside the magnetic field produces electromagnetic induction which results in production of electric energy.

Working of Electric Generator

Electric generator works on the concept of electromagnetic induction.

When the armature moves within the magnetic field an electric current is induced.
The direction of induced current changes, when the armature crosses the halfway mark of its rotation.
Thus, the direction of current changes once in every rotation.
Due to this, the electric generator usually produces alternate current, i.e. AC.
To convert an AC generator into a DC generator, a split ring commutator is used. This helps in producing direct current.

AC and DC current

AC – Alternate current: Current in which direction is changed periodically is called Alternate Current. In India, most of the power stations generate alternate current. The direction of current changes after every 1/100 second in India, i.e. the frequency of AC in India is 50 Hz. AC is transmitted upto a long distance without much loss of energy is advantage of AC over DC

DC – Direct current: Current that flows in one direction only is called Direct current. Electrochemical cells produce direct current.

DC current faces reduction in voltage during long distance transmission. This problem is solved by using AC current. So, AC current is ideal for long distance transmission. The current from power plants is supplied to households, factories and other establishments, in the form of AC current. This helps in preventing loss of power during long distance transmission.