3. ACKNOWLEDGEMENT
I wish to express my deep gratitude and sincere
thanks to the school senior Principal DR. VASANTHI
THIAGARAJAN, for her encouragement and provided
facilities for this school project. I sincerely
appreciate her generosity by taking me into his fold
for which I shall remain indebted to her. I extent my
appreciation to Ms. Janaki, my Physics teacher who
guided me to the successful competition of this
project. I take this opportunity to express my deep
sense of gratitude to her invaluable guidance,
ongoing encouragement, enormous motivation, which
has sustained my efforts at all, the stages of
project development.
I can't forget to offer my sincere thanks to my
classmates who helped me to carry out this project
successfully and for their valuable advice and last
but not least, I would like to thank CBSE for providing
this golden opportunity to investigate on this topic
and get to know many things.
5. OVERVIEW
Without transformers sending electricity to every
parts of the state or the country would be impossible.
It would have led to many loses both financially and
electrically.
The steps clearly depicts how electricity reaches our
home.
6. This process contains many sources like
hydroelectricity, thermal electricity, electricity from
wind, electricity due to nuclear reactions and so on…
Objective
To find the ratio of input and output voltages and
no. of turns in primary and secondary coils. And
also, to find the reason for stepping up and stepping
down the current voltages before it reaches our homes
or offices.
Introduction
Transformers are the primary devices that transfers electrical
energy from one electrical circuit to another circuit or multiple
circuits. A varying current in any coil of the transformer
produces a varying magnetic flux in the transformer's core,
which induces a varying electromotive force (EMF) across any
other coils wound around the same core.
7. The transformer is basically a voltage control device that is used
widely in the distribution and transmission of alternating
current power. The idea of a transformer was first discussed by
Michael Faraday in the year 1831 and was carried forward by
many other prominent scientific scholars. However, the general
purpose of using transformers was to maintain a balance between
the electricity fluctuation.
Theory
Electrical energy can be transferred between separate coils
without a metallic (conductive) connection between the two
circuits. Faraday's law of induction, discovered in 1831,
describes the induced voltage effect in any coil due to a changing
magnetic flux encircled by the coil. The generalpurpose of using
transformers was to maintain a balance between the electricity that
was generated at very high voltages and consumption which was
done at very low voltages. The transmission current is AC. The AC
current produces a varying magnetic flux in the transformer core.
This varying magnetic flux creates current in the secondary coil.
8. The transformer core is made up substance of infinitely high
magnetic permeability so that all of the magnetic flux passes
through it. This varying magnetic flux induces varying EMF.
According to Faraday’s law of induction, since the same magnetic
flux passes through both the primary and secondary windings in
an ideal transformer, a voltage in induced in each winding,
according to equation.
Vs = -Ns.dθ /dt in the secondary winding case, according to
equation.
Vp = -Np.dθ/dt the primary winding case.
The transformer winding voltage ratio is thus shown to be directly
proportional to the winding turns ration.
Vp/Vs = -Np/-Ns = α
Principle
Transformer works on the principle of mutual inductance.
There are two types of transformers:
9. • Step up and Step down transformer.
Step-up Transformer: They are used between the power generator
and the power grid. The secondary output voltage is higher than
the input voltage.
Step down Transformer: These transformers are used to convert
high voltage primary supply to low voltage secondary output.
Since the power is energy given out per second, it is source
dependent and it doesn’t change because of transformer. But
change in voltage and current is there.
Overall, a transformer carries the below operations:
1.Transfer of electrical energy from circuit to another
2.Transfer of electrical power through electromagnetic induction
3.Electric power transfer without any change in frequency
4. Two circuits are linked with mutual induction.
10. Losses in transformer:
Some energy is lost due to heating of copper wires used in the
primary and secondary windings. This power loss can be
minimized by using thick copper wires of low resistance.
The alternating magnetic flux induces eddy currents in the iron
core which leads to some energy loss in the form of heat. This loss
can be reduced by using laminated iron core.
Voltage transformation ratio:
K is called the voltage transformation ratio, which is a constant.
Case1: if N2 > N1, K>1 it is called a step-up transformer.
Case 2: if N2< N1, K<1 it is called a step-down transformer.
11. Requirements:
1. A transformer (used for led lights)
2. Voltmeter
3. Multimeter
4.Wire
Procedure:
1. We consider the input voltage for household appliances to be
in thee range of 220v to 230 v.
2. We use the voltmeter to measure the ratio of emf induced in
the primary coil and the secondary coil of the transformer
respectively.
3. Note the reading in voltmeter connected in output, so as to
read the output voltage and record the observations
accordingly in the form of tabular column.
4.Calculate the required the ratio as per the formula discussed
above.
5. Conclude from the observations and theory.
12. Observations:
Applications of transformers:
• The transformer transmits electrical energy through wires over
long distances.
• Transformers with multiple secondary’s are used in radio and
TV receivers which require several different voltages.
• Transformers are used as voltage regulators.
Conclusions
Normally a step-up transformer increases the voltage
proportional to the ration of the wounding of primary and
secondary coil. similarly step-down transformer does the same
but reduces the high voltage to the initial or required voltage. This
reduces heat losses and energy loss.
A step-up transformer had emf ratio greater than unity and a
step-down transformer had emf ratio less than unity.
The average ratio turns out to be 13.56 which tells that
transformer reduces the output voltage to nearly 13.5 times less
than the input voltage.
There is decrease in current whereas very high voltages are passed
to reduce the heat loss.
