An electric generator comes to our rescue when suddenly, we have a power cut during our birthday party. So, an electric generator provides us with electricity on which various appliances at our houses function. Automobiles, aircraft, ships, and trains all require electrical power generated by generators. This article will study electric generators, their types, properties, and working principles.

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What is an Electric Generator?

Electric Generator is a device that converts mechanical energy into electrical energy. The electricity being produced at various power stations is coming from the electric generator installed there. When a coil is rotated in the magnetic field, or there is relative motion between a coil and a magnet, an electromotive force (emf) or potential difference is induced in the coil.

Mechanical energy is required to rotate the coil and convert it into electrical energy. The induced emf is responsible for the flow of induced current through the coil, routed to our houses. The emf is induced due to a phenomenon known as electromagnetic induction.

Electric Generator Principle

Electric Generator works on the principle of electromagnetic induction. Electromagnetic induction is the phenomenon of the generation of electric current in a circuit by changing the magnetic flux linked with the circuit. 

Magnetic flux is the total number of magnetic field lines passing through a particular area. So, by relative motion between a coil and a magnet, we are changing the magnetic flux associated with the coil which in turn induces emf in the coil.

Faraday formulated two laws that explain the phenomenon of electromagnetic induction. They are:

1. Whenever the amount of magnetic flux linked with a circuit changes, an emf is induced in the circuit. The induced emf lasts so long as the change in magnetic flux continues.
2. The magnitude of emf induced in a circuit is directly proportional to the rate of change of magnetic flux linked with the circuit.

Various methods by which emf can be induced in a coil are as under:

1. By the relative motion between a coil and a magnet.
2. By the relative motion between a coil and a current carrying conductor.
3. By changing the magnitude of the current in the conductor placed near the coil.

The direction of the induced current so obtained in the coil can be found out using Fleming’s Right-Hand Rule that is as stated below:

“Stretch the thumb, the first finger, and the central finger of the right hand so that they are mutually perpendicular to each other. If the first finger points in the direction of the magnetic field, the thumb points in the direction of motion of the conductor, then the central finger points in the direction of induced current.”

In the electric generator, the coil is rotated in a magnetic field to get induced current. The induced current so obtained changes continuously in magnitude and periodically in direction several times in a second. Such a current is called alternating current \(AC\).

But when the current produced by the electric generator does not change in direction and magnitude then such a current is called direct current \(DC\). Based on the type of current obtained from the electric generator, we have types of generators.

Types of Electric Generator

Electric Generators produce \(AC\) as well \(DC\). Based on this the electric generators are classified as:

1. \(AC\) Generator: The current produced by this type of electric generator changes continuously in magnitude and periodically in direction several times in a second. Thus, the \(AC\) generator produces \(AC\). 

The frequency of \(AC\) in India is \(50{\rm{ Hz}}{\rm{.}}\) So, in India, \(AC\) completes \(50\) cycles in each second. In each cycle of \(AC\) the direction of the current is changed twice. That means,\(AC\) in India changes its direction every\({\frac{1}{{100}}^{th}}\) part of a second. Hence, in India \(AC\) changes direction every \(0.01\;{\rm{s}}\)

2. \(DC\) Generator: The current produced by this type of electric generator does not change its direction or magnitude. Hence, the frequency of \(DC\) is always zero.

\(AC\) generator and \(DC\) generator are much similar in their principle, construction and working except the replacement of slip rings as sliding contacts in \(AC\) generator with split ring or commutator in \(DC\) generator.

Electric Generator Diagram

Electric Generator construction can be shown with the diagram as given below:

Parts of Electric Generator

Electric Generator consists of various parts as mentioned under:

1. Armature: It consists of an insulated copper coil wound over a rectangular frame and soft iron core, which is laminated. 
2. Field Magnet: The magnetic field is supplied by a permanent magnet (in a small dynamo) and by an electromagnet in the case of a big commercial dynamo which is nothing but the electric generator that we are currently studying.
3. Slip rings (in \(AC\) generator): They are hollow metal rings held at different heights. One end of the armature is connected to one of the rings, and the other is connected to the other ring. These rings rotate with the rotation of the armature.
4. Split rings (in \(DC\) generator): Two halves of the same ring. The ends of the armature are connected to these halves of the same ring. These rings rotate with the armature.
5. Brushes or sliding contacts: These are flexible metal plates or carbon rods. They are in constant touch with the rings. They help pass the induced current from the armature and the rings to the external circuit.

Electric Generator Working

Electric Generator produces electric current by rotating the coil in the magnetic field. The working of an electric generator is described below:

The armature placed between the poles of the magnet is rotated. When the armature is rotated anticlockwise, the left arm of the armature will move inwards, and the right arm of the armature will move outwards. Applying Fleming’s Right-Hand Rule, we find that the induced current in the armature coil is in the anticlockwise direction. So, the direction of the induced current in the external circuit will be in the anticlockwise direction. 

The connection of the external circuit is established with the help of the slip ring and the sliding brushes that is connected to the ends of the external circuit. In an AC generator, the connection of the external circuit with the specific ends of the armature coil is maintained throughout the rotation. 

But in the \(DC\) generator due to the split rings changing their connection with the brushes, the ends of the external circuit changes their connection with the ends of the armature coil. After the armature coil has turned through \({180^ \circ }\) the left arm of the armature coil will take the position of the right arm and vice versa. By continuing the rotation in the same direction (anticlockwise), the now left arm which was the right arm earlier will move inwards and the other arm will move outwards. 

Again, by applying Fleming’s Right-Hand Rule, we find that the induced current in the armature coil is in the anticlockwise direction. But now as the ends of the armature coil has maintained their connection with the same ends of the external circuit, the direction of the induced current in the external circuit will now be in a clockwise direction. 

Thus, in the \(AC\) generator, we see that the direction of induced current changes in the external circuit after every half revolution of the armature coil. Hence, the induced current is alternating in nature. Moreover, the magnitude of the induced current also varies due to the varying angle between the armature coil and the magnetic field lines.

In \(DC\) generator, the ends of the armature coil change their connection with the ends of the external circuit with the help of split rings. So, the direction of induced current maintains its direction in the external circuit to be the anticlockwise direction. Thus, in \(DC\) generator the induced current does not change its direction and hence is not alternating in nature rather it is direct in nature.

The magnitude of the induced emf in a generator can be increased by:

1. increasing the number of turns of its armature coil
2. increasing area of the armature coil
3. increasing speed of rotation of the armature coil
4. increasing the strength of the magnetic field.

Now, based on the need to induce \(AC\) or \(DC\) as well as the magnitude of the induced current to be obtained, we choose the type and size of the generator to be installed. 

Electric Generator Applications

An electric generator finds its applications in many places. It produces electricity that is the most versatile form of energy and is needed at a massive scale during our day-to-day activities. Some of them are mentioned as under:

1. Electric generator is installed at windmills of the wind farm for large scale production of electricity using wind energy. In such a case, the wind energy is converted into mechanical energy and converted into electrical energy.

2. An electric generator is installed at geothermal power stations wherein the geothermal energy is utilised to heat water. The steam so generated rotates the turbine, and hence the geothermal energy is converted into mechanical energy and finally into electrical energy.

3. Electric generators are installed at hydroelectric power stations. The water gushing through the dam’s gates rotates the turbine and produces electricity with the help of an electric generator. Here, the kinetic energy of the flowing water is converted into mechanical energy, which is later converted into electrical energy.

4. Electric generators are installed at nuclear power stations. The nuclear reactor at the nuclear power station supplies the energy to produce steam for rotating the turbine to produce electricity using an electric generator. Here, the energy obtained from the nuclear chain reaction is converted into mechanical energy and then to electrical energy using an electric generator.
5. Electric generators are installed at thermal power stations. Here, coal and petroleum are burnt to heat water to produce steam. This steam rotates the turbine that further produces electricity. Hence, heat energy obtained from burning fossil fuels is converted into mechanical energy, further converted into electrical energy using an electric generator.
6. An electric generator is installed at the power plants to extract energy from the sea. Energy from the sea in the form of tidal energy, wave energy, and ocean thermal energy is extracted to run the turbine to produce electricity with the help of an electric generator. Here, the energy stored in the sea is derived by various means and then converted into mechanical energy, further converted into electrical energy using an electric generator.

Summary

We hope this article helped you understand the principle, types, construction, and working of an electric generator. Also, it gave an idea about the places where an electric generator is used to supply us with electricity for our day-to-day needs. You could also learn the diagrams and parts of an electric generator with its applications.

FAQs

Q.1.What are the advantages of \(AC\) over \(DC\)?
Ans: The advantages of over \(DC\) are as under:
1. \(AC\) can be obtained at any desired voltage with the help of a transformer.
2. Wastage of power during transmission is less while using \(AC\).
3.\(AC\) machines are stout and durable that require less maintenance.

Q.2. What is the principle on which electric generator works?
Ans: Electric generator works on the principle of electromagnetic induction.

Q.3. What is a commutator?
Ans: It is a device that connects the armature of a \(DC\) generator with the external circuit and helps in maintaining the direction of current in the external circuit. It changes the connection of the armature ends with the ends of the external circuit after every half a revolution.

Q.4. What is electromagnetic induction?
Ans: Electromagnetic induction is the phenomenon in which current is induced in a circuit by changing the magnetic flux associated with it.

Q.5. What is an electric generator?
Ans: Electric generator is a device that converts mechanical energy into electrical energy.

Q.6.What are the disadvantages of \(AC\) over \(DC\)?
Ans: \(AC\) is more dangerous than \(DC\) as it attracts a person and may give a serious shock or may even electrocute. Moreover, \(AC\) cannot be used for electroplating, electrotyping and other such electrolytic processes where only \(DC\) can be used.

Q.7. Which rule is used to find the direction of current induced in an electric generator?
Ans: To find the direction of current induced in an electric generator, Fleming’s Right Hand Rule is used.

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