3. What is A.C voltage and Current ?
An alternating current is the current which changes periodically
both in magnitude and direction.
4. What is Generator?
The machines which are used to generate electrical voltages are called
“GENERATORS”.
This is the figure of AC Generator Nikola Tesla
-Inventor of A.C Generator
5. 1. By rotating the coil inside the uniform magnetic field at constant
speed
2. By rotating the magnetic field around the stationary coil at the
constant speed
The alternating voltage is generated in two ways.
In small AC generators, the coil rotates between the magnetic field, whereas in large ac generator the
magnetic field rotates around the coil because of some economical consideration.
6. This Figure is one type of Generators. When the Coil is rotated between the
Poles of the Magnet by cranking the handle, an AC Voltage Waveform is produced.
The amount of current depends on:
1. The speed at which the conductor experiences a changing magnetic field,
2. The number of coils that make up the conductor, and
3. The position of the plane of the conductor with respect to the magnetic field.
7. Operation principle of a Generator is based on Electromagnetic Induction,
which is defined by Faraday's Law, which states:
Eemf is the Electromotive Force,
N,is the number of turns,
dΦ / dt is the Rate of Change of
Magnetic Flux
8. Structure of generetor:
An Ac generator consists of two poles i.e is the north
pole and south pole of a magnet so that we can have a
uniform magnetic field.
There is also a coil which is rectangular in shape that is
the armature.
These coils are connected to the slip rings and attached
to them are carbon brushes.
The rectangular coils rotate about an axis which is
perpendicular to the magnetic field. There is also a
shaft which rotates rapidly.
9. The direction of the current changes with every half turn of the coil. As one side of the
loop moves to the other pole of the magnetic field, the current in the loop changes
direction. This type of current which changes direction is known as alternating current
and the Figure shows how it comes about as the conductor rotates.
Figure:The red (solid) dots represent current coming out of
the page and the crosses show current going into the page.
10. Steps in the operation:
Coil starts in reference
position 0∘0∘: The plane of the
coil is perpendicular to the
magnetic field lines.
Coil gets turned to reference
position 90∘90∘: The plane of the
coil is parallel to the magnetic
field lines.
Coil gets turned to reference
position 180∘180∘ and 360∘360∘:
Same as the analysis in reference
position 0∘0∘.
Coil gets turned to reference
position 270∘270∘: Same analysis
as in reference
position 90∘90∘ BUT the e.m.f. is
in the opposite direction.
11. 1. Decrease distance between magnet and coil. (To increase magnetic
field strength experienced by coil)
2. Use a stronger magnet.
3. Increase frequency of rotation of the coil.
4. Increase number of turns in the coil.
Ways to increase emf in a.c. generator:
