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Physics Investigatory Project 2
Project Work (MIT School of Distance Education)
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PHYSICS INVESTIGATORY
PROJECT
NEW GREEN FIELD PUBLIC ACADEMY
SESSION 2022-23
CLASS-XII
TOPIC: APPLICATIONS OF SELF-INDUCATANCE
SUBMITTED BY: ARHAT RAMPURIA
SUBMITTED TO: Mr. RAHUL RATHOR
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CERTIFICATE
This is to certify that Arhat Rampuria of New
Green Filed Public Academy has completed
the Investigatory Project in Physics titled
“Study of Applications of Self-Inductance”
himself under the supervision and guidance of
Physics Teacher Mr. Rahul Rathor during the
year 2022-23.
1.) Internal Examiner
2.) External Examiner
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ACKNOWLADGEMENT
First of all, I am deeply thankful to my
Physics teacher Mr. Rahul Rathor for
extending his valuable and scholarly guidance
throughout the preparation of this project. I am
also thankful to all my respected teachers,
library staff, office staff and staff members of
the Physics Laboratory of the school. I am also
thankful to the teachers and staff members of
the department of Physics for extending their
humanitarian and scholastic assistance in
finding out the solutions of some query during
my work. Last but not the least I am indebted
to my friends, classmates and parents for
encouraging and never let me down in my
confidence while completing the project.
INTRODUCATION
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What is self-inductance?
•When an electric current is passed through an
insulated conducting coil, it gives rise to a
magnetic field in the coil so that the coil itself
behaves like a magnet.
•The magnetic flux produced by the current in
the coil is linked with the coil itself.
•As the strength of the current in the coil is
changed, the flux linked with the coil also
changes. Under such circumstances an emf is
induced in the coil too. Such emf is called a
self-induced emf and this phenomenon is
known as self-induction.
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AIM:To study the factor on which the self
inductance of a coil depends by observing
the effect of this coil, when put in series with
a resistor (bulb) in a circuit fed up by an
A.C. source of adjustable frequency.
APPARATUS:A coil of large turns, a.c. source of adjustable
frequency, an electrical bulb , (6V) a.c.
ammeter of suitable range rheostat , a soft
iron rod, one way key, connecting wires etc.
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THEORY:Self inductance is the property of a coil which
opposes the change in current through it. The
self inductance of a coil (long solenoid) is
L= µ0 µrN2A/ l
Where µr, = Relative magnetic permeability of
magnetic material,
µr = µ/ µ0
N = Total number of turns in solenoid
A = Area of cross-section of solenoid
l= length of solenoid.
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Hence, the self inductance depends upon:
1.
No. of turns (N), Lα N²
2. Geometry of coil, Lα A, L α(1/l)
3. Nature of core material, Lα µ
When an inductor is connected in series with a
resistor (bulb) with a variable source of
frequency, then current flowing in the bulb is
Irms = Erms/Z
Where, Z = √ R2 + ω2 = Impedance of the a.c.
circuit. Here
R=
Resistance of the bulb
L = Self inductance of coil
ω = 2πf = Angular frequency of a.c. source
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CIRCUIT DIAGRAM :-
PROCEDURE:1. Make all connections as shown in the
circuit diagram.
2. Switch on the a.c. supply & adjust the
current in the circuit by using the variable
resistor (Rh).
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3. Record the current in a.c. ammeter & seethe
brightness of bulb.
4. Now, put the soft iron rod inside the
conductor core & record the current in a.c.
ammeter & again check the brightness of
bulb. The current & brightness both
decreases.
5. Now, switch off the supply & decrease the
frequency of a.c. source (say 50 Hz).
6. Again switch on the supply & adjust the
current in circuit at same constant voltage 6 V
by using the rheostat. Note the current in
ammeter & brightness of bulb. The current &
brightness both will increase.
7. Again insert the iron rod in the core of coil
& note the current & brightness. The current
& brightness both decreases.
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8. Repeat the steps 5, 6 and 7 for different
frequency of a.c. source.
OBSERVATIONS:1. Least count of ammeter = 0.05 A.
2. Zero error of ammeter = 0 A.
3. Range of ammeter = 0 – 5 A
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RESULT :1. The current in the circuit decrease on
inserting the iron rod in the core of coil at
constant frequency of applied voltage
&brightness of bulb decreases & vice-versa.
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2. The current in the circuit increases on
decreasing the frequency of applied voltage &
vice-versa. Therefore, the brightness of bulb
increases.
PRECAUTIONS:1. The coil should have large number of
turns.
2. Current should be passed for a small time
to avoid the heating effect.
SOURCES OF ERRORS :1. The resistance of circuit may increases
lightly due to heating effect of current.
2. There may be eddy current in soft iron
coil.
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Applications of Self-Inductance
There are many applications of self
inductance, one of the major ones being a tesla
coil,
What is a tesla coil
A Tesla coil is a radio frequency oscillator that
drives
the
air-core
double-tuned
resonant transformer to produce high voltages
with low currents.
To understand better, let’s define what is a
radio frequency oscillator. Primarily, we are
aware that the electronic oscillator is a device
that produces electrical signals of either a sine
wave or a square wave. This electronic
oscillator produces signals in the radio
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frequency range of 20 kHz to 100 GHz,
known as a radio frequency oscillator.
Tesla Coil Working Principle
This coil has the ability to produce output
voltages up to several million volts based upon
the size of the coil. The Tesla coil works on a
principle
to
achieve
a
condition
called resonance. Here, the primary coil emits
huge amounts of current into the secondary
coil to drive the secondary circuit with
maximum energy. The fine-tuned circuit helps
to shoot the current from primary to secondary
circuit at a tuned resonant frequency.
Tesla Coil Circuit Diagram
This coil has two main parts – a primary coil
and a secondary coil, with each coil having its
own capacitor. A spark gap connects the coils
and capacitors. The functionality of the spark
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gap is to generate the spark to excite the
system.
Tesla Coil Working
This coil uses a specialized transformer called
a resonant transformer, a radio-frequency
transformer, or an oscillation transformer.
The primary coil is connected to the power
source and the secondary coil of a transformer
is coupled loosely to ensure that it resonates.
The capacitor connected in parallel with the
transformer circuit acts as a tuning circuit or
an LC circuit to generate signals at a specific
frequency.
The primary of the transformer, otherwise
referred to as a resonant transformer steps up
to generate very high levels of voltage ranging
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between 2kv to 30 kV, which in turn charges
the capacitor. With the accumulation of
massive amounts of charge in the capacitor,
eventually, breaks down the air of the spark
gap. The capacitor emits a huge amount of
current through the Tesla Coil (L1, L2), which
in turn generates a high voltage at the output.
Oscillation Frequency
The combination of a capacitor and primary
winding ‘L1’ of the circuit forms a tuned
circuit. This tuned circuit ensures that both
primary and secondary circuits are finely
tuned to resonate at the same frequency. The
resonant frequencies of the primary ‘f1’ and
secondary circuits ‘f2’ and are given by,
f1=1/2π√L1C1 and f2=1/2π√L2C2
As the secondary circuit cannot be adjusted,
the moveable tap on ‘L1’ is used to tune the
primary circuit till both the circuits resonate at
the same frequency. Therefore, the frequency
of the primary is the same as the secondary.
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f = 1/2π√L1C1 =1/2π√L2C2
The condition for primary and secondary to
resonate at the same frequency is,
L1C1= L2C2
The output voltage in the resonant transformer
does not depend on the number-of-turns ratio
as in ordinary transformer. As soon as the
cycle begins and as the spar sets up, the
primary circuit’s energy is stored in the
primary capacitor ‘C1’ and the voltage at
which the spark breaks down is ‘V1’.
W1=1/2C1V12
Similarly, the energy at the secondary coil is
given by,
W2=1/2C2V22
Assuming there is no loss of energy, W2 =
W1. Simplifying the above equation, we get
V2 = V1√C1/C2 = V1√L2/L1
In the above equation, the peak voltage can be
achieved when air breaks down do not occur.
The peak voltage is the voltage at which the
air breaks down and begins to conduct.
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Advantages/Disadvantages of Tesla Coil
The advantages are
 Allows uniform distribution of voltage
throughout the winding coils.
 Builds up the voltage at a slow pace and
hence no damage.
 Great performance.
 The use of 3-phase rectifiers for higher
powers can offer tremendous load
sharing.
The disadvantages are
 Tesla coil poses several health hazards
due to high voltage radio frequency
emission that includes skin burn, damage
to the nervous system and heart.
 Involves high costs in buying large DC
smoothing capacitor.
 Construction of circuit consumes much
time as it needs to be perfect to resonate
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Applications of Tesla Coil
At present, these coils do not require large
complex circuits to produce high voltage.
Nevertheless, small Tesla coils find their
applications in a range of sectors.
 Aluminium welding
 Cars use these coils for the spark plug
ignition
 Created Tesla coil fans, used to generate
artificial lighting, sounds like music
Tesla coils in Entertainment and
Education industry are used as attractions
at electronics fairs and science museums
 High vacuum systems and arc lighters
 Vacuum system leak detectors
1). What do Tesla coils do?
This coil is a radio frequency oscillator that
drives a resonant transformer to generate a
high voltage at low current.
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2). Can a Tesla coil charge a phone?
Nowadays, smartphones are released with
built-in wireless charging, which uses the
principle of a Tesla coil.
3). Is Tesla coil dangerous?
The coil and its equipment are very dangerous
as they produce very high voltages and
currents which cannot be ensured by the
human body
4). Why do tesla coils make music?
Generally, this coil converts air around it into
a plasma that changes volume and causes the
waves to spread across all the directions,
creating sound/music. This happens at a high
frequency of 20 to 100 kHz.
5). How did Tesla transmit electricity
wirelessly?
A spark gap is used to connect the capacitors
and two coils. As the power is fed in through a
transformer, it produces the necessary current
and powers the entire circuit.
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Thus, this is all about an overview of the Tesla
coil that can be used to generate electricity of
high voltage, low current, and high-frequency.
Tesla Coil has the ability to transmit electricity
wirelessly up to several kilometres. We
ensured that this article gives the reader
insights into the working of the Tesla coil,
advantages
and
disadvantages,
and
applications. Truly, his invention of wireless
transmission of electric energy has changed
the way the world communicates.
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Bibliography
Sites used:
https://www.elprocus.com/what-is-tesla-coilcircuit-diagram-working-its-applications/
https://www.slideshare.net/karan_19951/selfinductance-40498923
Ncert class 12 Textbook
Physics Lab Manuel
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