CERTIFICATE
This is to certify that Ruchika Thakur, a
student of Class XII has successfully
completed the project under the guidance
of Mr. Ritesh Rai during the academic
year 2024-25 in partial fulfillment of
physics practical examination conducted
by CBSE.
Sub Teacher Principal Examiner
ACKNOWLEDGEMENT
I would like to express my sincere gratitude to
all those who have contributed to the
successful completion of this physics project.
Special thanks to my physics teacher, [Mr.
Ritesh Rai], for their guidance and support
throughout the project. I also appreciate the
help from my classmates and friends who
provided valuable insights and encouragement.
Finally, I thank my family for their unwavering
support and motivation.
This project has been a great learning
experience, and I hope it reflects my dedication
and hard work.
INDEX
S.NO. CONTENTS PAGE NO.
1 Introduction 1
2 Principle of AC Generator 2
3 Construction of AC Generator 3
4 Theory 4
5 Working of AC Generator 5
6 Expression for instantaneous emf 6-7
produced
7 Application of AC Generator 8
8 Bibliography 9
INTRODUTION
AC Generator means Alternating current
generator. It is a device which is used to
convert mechanical energy into electrical
energy. A.C. generator forces electric current
to flow through an external circuit. The source
of mechanical energy may be a reciprocating or
turbine steam engine, water falling through a
turbine or waterwheel, an internal combustion
engine, a wind turbine, a hand crank,
compressed air, or any other source of
mechanical energy.
PRINCIPLE OF AC
GENERATOR
It is based on the principle of electro-
magnetic induction, i.e., whenever
amount of magnetic flux linked with a
coil changes, an e.m.f. is induced in the
coil. The direction of current induced is
given by Fleming's right-hand rule.
CONSTRUCTION OF AC
GENERATOR
The A.C. Generator is consist of four main parts:
(1) THE COIL (ARMATURE) :
A rectangular coil ABCD consist of a large number of turns of
copper bound over a soft iron core is called armature. The soft
iron core is used to increase the magnetic flux.
(2) MAGNETIC FIELD :
It is usually a permanent sponge magnet having concave poles.
The armature is rotated of a magnet so that axis of the
armature is perpendicular to magnetic field lines.
(3) SLIP RINGS:
Slip rings are the magnetic rings, which are connected to the
terminal of the armature. These rings are rotated with the coil
and these are used to draw the current from the generator.
(4) BRUSHES:
The brushes B1 & B2 just touches the slip rings. They are not
rotating with the coil and these brushes lead to the output of
load resistance.
THEORY
1. The strong magnetic field is produced by a current flow through
the field coil of the rotor.
2. The field coil in the rotor receives excitation through the use of slip
rings and brushes.
3. Two brushes are spring-held in contact with the slip rings to
provide the continuous connection between the field coil and
external circuit.
4. The armature is contained within the windings of the stator and is
connected to the output.
5. Each time the rotor makes one complete revolution, one complete
cycle of AC is developed.
6. A generator has many turns of wire wound into the slots of the
rotor.
7. The magnitude of AC voltage generated by an AC generator is
dependent on the field strength and speed of the rotor.
8. Most generators are operated at a constant speed ; therefore , the
generated voltage depends on field excitation or strength.
WORKING OF AN AC GENERATOR
The coil is rotated in the anti-clockwise direction. In the first
half rotation the arm AB is moving outward and CD is moving
inward. So the e.m.f. is induced in the arm AB from A to B.
And in the arm CD from C to D. After half rotation (in the
second half). The arm CD is moving outward and AB is
moving inward. In this time current is induced in arm CD from
D to C. And in arm AB from B to A. In the second-half
rotation, the current direction is changing so in this generator
AC is produced.
EXPRESSION FOR INSTANTANEOUS
EMF PRODUCED
Let position of the coil at any time t. It's
making Ɵ with vertical. If w is uniform
angular speed of the coil.
Then, Ɵ =wt
B be the strength of magnetic field n be
the number of turns in the coil and A area
of the coil then magnetic flux with the coil
in this position is given by:
Φ = nBA Cos Ɵ = nBA Cos wt
APPLICATIONS OF
AC GENERATOR
1. Aircraft auxiliary power generation, wind generators, high-
speed gas turbine generators.
2. Hybrid electric vehicle (HEV) drive systems, automotive
starter generators.
3. An ac generator, or 'alternator', is used to produce ac
voltages for transmission via the grid system or, locally, as
portable generators.
4. All of our household appliances run on ac current.
Ex: Refrigerator, washing machines, oven, lights, fan, etc.
5. The main advantage of AC is ease of power distribution.
It is more efficient to use high voltage to distribute power, but
it is not safe to have high voltage at home. It is easy to step up
(and step down) AC voltage using a transformer.
BIBLIOGRAPHY
• CBSE Lab Manual
• NCERT Textbook
• Websites
1. www.google.com
2. www.youtube.com
