Explanation of Electric Generator

The Electric Generator and Power Supply  

Introduction

Faraday’s discovery gave birth to the phenomenon of electromagnetic induction. Electromagnetic induction is the phenomenon where a current is induced in a circuit due to a change in the magnetic flux linked to it. Many devices work on electromagnetic induction like speakers, transformers, and electric generators. An electric generator is a device that generates electricity by the process of electromagnetic induction. It converts mechanical energy into electrical energy.  

An electric generator is of two types. 

• AC generator  
• DC generator 

Explanation

Parts of an AC generator: 

Armature: It is a rectangular coil of insulated copper wire. 

Magnets: A couple of magnets that produce a uniform magnetic field. 

Rings: Two circular slip rings R1 and R2.  

Axle: The rings are placed on the axle, which can rotate freely. 

Brushes: The rings are connected to two conducting Brushes B1 and B2; these brushes are made up of carbon. 

Galvanometer: A galvanometer is used to measure the current and its direction. 

Working of an AC generator: 

Step -1 

The axle is rotated such that it moves in the clockwise direction, the left side (AB) of the rectangular coil moves up, and the right side (CD) moves down. 

According to Fleming’s Right-Hand Rule, the induced current is set up in the coil clockwise along the loop as B2→CDAB→B1. This means, in the external circuit, current flows from B1 to B2. 

Step -2 

After half rotation, the side (CD) of the rectangular coil moves up, and the side (AB) moves down. 

According to Fleming’s Right-Hand Rule, the induced current is set up in the coil clockwise along the loop as B1→BAD C→B2. This means in the external circuit current flows from B2 to B1. 

Here we see that after every half rotation of the rectangular coil, the induced current changes it’s direction. This is called an AC current or alternating current. 

This type of generator is known as an AC generator. 

Construction of a DC generator: 

In order to convert an AC generator into a DC generator, the two slip rings are replaced with a commutator-type split ring. 

Parts of a DC Generator: 

Armature: It is a rectangular coil of insulated copper wire. 

Magnets: A couple of magnets that produce a uniform magnetic field. 

Split rings type commutator segments: They reverse the direction of current 

Brushes: Split rings are connected to conducting Brushes B1 and B2. 

Axle: The rings are placed on the axle, which can rotate freely. 

Galvanometer: A galvanometer is used to measure the current and its direction. 

The working of a DC generator: 

Step -1 

The axle is rotated such that it moves in the clockwise direction, the left side (AB) of the rectangular coil moves up, and the right side (CD) moves down. 

According to Fleming’s Right-Hand Rule, the induced current is set up in the coil clockwise along the loop as R2→CDAB→R1. The R1 is in contact with B1, and R2 is in contact with B2. This means, in the external circuit, current flows from B1 to B2. 

Step -2 

After half rotation, the split ring R1 will touch brush B2, and ring R2 will touch with B1; also, the side (CD) of the rectangular coil moves up, and the side (AB) moves down. 

According to Fleming’s Right-Hand Rule, the induced current is set up in the coil clockwise along the loop as R1→BADC→R2. The R1 is in contact with B2, and R2 is in contact with B1. This means, in the external circuit, current flows from B1 to B2 again. 

Here we see that after every half rotation of the rectangular coil, the induced current does not change its direction in the external circuit. This is called a DC current or direct current. 

This type of generator is known as a DC generator. 

Difference between AC and DC current: 

• It is better to transmit AC power than DC power. 
• DC power is supplied at a constant voltage. Whereas AC power can be stepped up (increased) or stepped down (decreased) to supply the required voltage. 

Transformer: 

AC voltage is stepped up and stepped down using a transformer. 

Transformer works on electromagnetic induction. When AC power is supplied to the coils of the transformer, magnetic flux is linked continuously due to variation in AC current changes as the AC current continuously changes so. 

If we supply DC current to a transformer, the magnetic flux does not change as DC current does not change in direction. A transformer does not work effectively in the case of DC supply. 

Step-up transformer 

A step-up transformer converts low AC voltage into high AC voltage as the primary coil has fewer turns than the secondary coil. 

Step-Down Transformer 

A step-down transformer converts high AC voltage into low AC voltage as the primary coil has more turns than the secondary coil. 

Use of generators at power stations: 

At power stations, generators are used to produce electricity on a large scale. In order to move the coil in the magnetic field, mechanical energy is provided by rotating turbines. 

The Turbines are Powered by: 

Thermal power plants: Thermal power stations use steam produced by burning coal, oil gas, nuclear power, etc.; the turbines are rotated at a high speed. 

Windmills: In some places, turbines are rotated by a windmill to drive a generator. 

Hydroelectric power station: In hydroelectric power stations, the water from the reservoir rushes into the powerhouse to spin the turbine, which drives the generator to produce electricity.

Summary

• An electric generator is a device that generates electricity by the processes of electromagnetic induction.
• An electric generator is of two types AC generator and DC generator. An AC generator produces AC power, and a DC generator produces DC power.
• In order to convert an AC generator into a DC generator, the two slip rings are replaced with a commutator-type split ring.
• The direction and magnitude of alternating current(AC) change with time whereas the direction of direct (DC) current remains fixed it’s magnitude may change.
• It is easy to transmit AC current than DC current. DC power is supplied at constant voltage. Whereas AC power can be stepped up (increased) or stepped down (decreased) to supply the required voltage.
• AC voltage is stepped up and stepped down using a Transformer.
• Transformer works on electromagnetic induction. A transformer is of two types step-up transformer and step-down transformer.
• A step-up transformer converts low AC voltage into high AC voltage as the primary coil has fewer turns than the secondary coil.
• A step-down transformer converts high AC voltage into low AC voltage as the primary coil has more turns than the secondary coil.
• At power stations generators are used to produce electricity at a large scale. In order to move the coil in the magnetic field mechanical energy is provided by rotating turbines.
• The turbines are powered by:
• Steam produced by thermal power plants