Describe the principle construction and working of an AC generator. Draw neat labeled diagram

AC Generator Principle?

Based on the phenomenon of electromagnetic induction

**Construction**

**Main parts of an ac generator:**

- Armature? Rectangular coil ABCD
- Filed Magnets? Two pole pieces of a strong electromagnet
- Slip Rings? The ends of coil ABCD are connected to two hollow metallic rings R 1 and R2.
- Brushes? B1 and B2 are two flexible metal plates or carbon rods. They are fixed and are kept in tight contact with R1 and R2 respectively.

**Theory and Working** ? As the armature coil is rotated in the magnetic field, angle *?* between the field and normal to the coil changes continuously. Therefore, magnetic flux linked with the coil changes. An *emf* is induced in the coil. According to Fleming�s right-hand rule, current induced in AB is from A to B and it is from C to D in CD. In the external circuit, current flows from B2 to B1.

To calculate the magnitude of *emf* induced:

Suppose

A? Area of each turn of the coil

N? Number of turns in the coil

? Strength of magnetic field

?? Angle which normal to the coil makes with at any instant *t*

? Magnetic flux linked with the coil in this position:

= *NBA* cos *?* = *NBA* cos *?* *t* �(i)

Where � *?* � is angular velocity of the coil

As the coil rotates, angle *?* changes. Therefore, magnetic flux *?* linked with the coil changes and hence, an *emf* is induced in the coil. At this instant t, if e is the *emf* induced in the coil, then? e = NAB? sin? t