Question

What do you mean by electric generator? Differentiate between a.c and d.c generators on the basis of construction?

Answer 1

Hint:Generator is the device which converts magnetic energy into electric energy. Alternating current and direct current are two forms in which current is produced. current which varies with time is termed as alternating current and which remain constant with time is direct current.

Step by step solution
A generator is an electrical machine that transforms mechanical energy provided by the prime mover into electrical energy. The prime mover can be steam, water, gas turbine, wind turbine, etc.

Working principle of generator

The operation of an electrical generator depends on the faraday law of electromagnetic induction.

That says if a conductor is put into the field then the voltage induces in that conductor. In the case of the generator, the conductor is the rotor of a generator and the field is provided by the stator of the generator.

We can use Fleming rule to find the direction of the voltage induced by that conductor. That explains that if we arrange our right-hand first finger, second finger, and thumb in a such a way that these are at 90⁰ to each other, and we suppose that motion of conductor is along the thumb, first finger is in the direction of field then the second finger will show the direction of voltage induces in the conductor.

The working principle of both ac and dc generators is similar but the difference is that in dc generator commutators are used to provide a dc output.


Difference between AC and DC generator on the basis construction as under:

S.NO	AC GENERATOR CONSTRUCTION	DC GENERATOR CONSTRUCTION
1.	There is no need for commutators in the construction of AC generators.	In DC generator, commutators are used
2.	In an AC generator, slip rings are used.	In this generator split rings are used for conversion of AC into DC at the output terminals.
3.	In ac, generator armature is always existing at the rotor.	In dc generators the armature part can be either rotor or stator.
4.	Cost of construction is high	Cost of construction is relatively less

Note:Two find the direction of current in circuit Fleming’s right-hand used which states that, stretch the forefinger, the middle finger and the thumb of the right hand such that they are manually perpendicular to each other. If the forefinger indicates the direction of the magnetic field, rhumb indicates the direction of the motion of the conductor. The middle finger indicates the direction of the induced current in the conductor.