Electric Generator

Q. 1    Define

Ans. a) Electric generator – An electric device which converts mechanical energy into electric energy is called an electric generator.

b)    A.C. generator – A generator which converts mechanical energy into electric energy in the form of an alternating current (A.C.) is called an A.C. generator.

c)    D.C. generator – A generator which converts mechanical energy into electric energy in the form of a direct current (D.C.) is called a D.C. generator.

Q. 2     On which principle the working of an electric generator is based?

Ans.     Principle of an electric generator :- Electric generator works on the principle of electromagnetic induction. When the coil of electric generator rotates in a magnetic field the magnetic field induces a current in this coil. This induced current then flows into the circuit connected to the coil.

«Q. 3   Explain the construction & working of an electric generator.

Ans.     An electric generator is a device used to convert mechanical energy into electrical energy. It works mainly on the principle of electromagnetic induction. There are two types of electric generators. 1. A.C. generator & 2. D.C. generator.

I.          Electric A.C. generator :

A]        Construction :- The main parts of an A.C. generator are –

            i. Armature coil (ABCD)                    ii. Strong magnets (N & S)

            iii. Split rings (Brass ring R₁ & R₂)     iv. Carbon Brushes (B₁ & B₂)

                                             Fig. Electric AC generator 

          A,B,C,D     – Armature coils

N & S        – Poles of magnet

R₁ & R₂      – Rings

B₁ & B₂      – Carbon brushes

G             – Galvanometer

B]        Working of A.C. generator : When the armature coil rotates in the magnetic field of strong magnets, it cuts magnetic lines of force. Thus, a potential difference is set up & an induced current is set up in the coil. The direction of the induced current is according to  Flemings right hand rule. In half a rotation of the coil, the current flows through the brush B₁ in one direction. In the other half rotation, the current flows through the brush B₂ in the opposite direction. This process is repeated & the induced current is an alternating current.

II.        Electric D.C. generator or Dynamo.

A]        Construction – The main parts of D.C. generator are

            i) Armature coil (ABCD)        ii) Strong magnets (N & S)

            iii) Split rings (R₁ & R₂)          iv) Carbon Brushes (B₁ & B₂)  v) Bulb.

                          Fig. Electric D.C. generator

ABCD    – Armature coils

N & S    – Poles of magnet

R₁ & R₂  – Rings

B₁ & B₂  – Carbon brushes

B           – Bulb

B]        Working of  a D.C. generator : The D.C. generator is provided with a bulb connected across the carbon brushes. The glowing of the bulb shows the output. When the coil of a D.C. generator rotates in a magnetic field, a potential difference is set up. This causes the flow of a current. The current is in the same direction because one brush is always in contact with the arm of the armature moving downwards in the magnetic field. Thus the current generated is flowing in the same direction & is a direct current.

«Q. 4             Distinguish between Electric motor & electric generator.

Electric motor

Electric generator

i.     Electric motor converts electrical energy into mechanical energy. ii.    The principle of a motor is that a conductor carrying a current placed in a magnetic field experience a force. iii.   A source of current supplies an electric current to the armature coil. iv.  Electric motor is used in many common appliances such as electric fans, hairdryers, grinders, blenders, etc.

i.        Electric generator converts mechanical energy into electrical energy. ii.    The principle of a generator is that when the coil of the generator rotates in a magnetic field, an induced current flows in the circuit. iii.   There is no source of current, but a bulb is introduced between the carbon brushes to check the output, when the generator rotates. iv.  Electric generator is mainly used in buildings, hospitals, etc. to generate power especially when there is a power failure.

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