Chapter-6|Electromagnetic Induction (EMI)| NCERT 12th Physics:
AC Generator:
AC generator is a kind of device that produces electrical energy from mechanical work.
Principle: An AC generator is based on the phenomenon of electromagnetic induction, which is state that whenever magnetic flux linked with a conductor or coil changes an EMF is induced in the coil.
Construction: Construction of AC generator are as follows.
Armature:- A rectangular coil ABCD consisting of a large number of turns of copper wire wound over a soft iron core is called armature.
Field Magnet:- Two poles pieces of a strong electromagnet.
Slip Rings:- The end of the coil ABCD are connected to two hollow metalic Rings, Ring1 and Ring2 called slip rings.
Brushes:- Two brushes B1 and B2 are two flexible metal plates or Carbon rods. They are fixed and are kept in slight contact with rings R1 and R2.
Working:
As the armature of the coil rotated in the uniform magnetic field, angle theta between the field and the normal to the coil changes continuously.
Therefore, magnetic flux linked with the coil changes and an EMF is induced in the coil. According to the Fleming left hand rule, current induced in AB is from B to A (In first half rotation).
Calculation of Magnitude of Induced EMF and Current:
We know that the magnetic flux linked with each tern of the coil
