Factors on which self
inductance of coil
depend
Objective
To study the factors 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.
I would like to express my special thanks
of gratitude to my teacher Mrs. A. Uma
and our Principal Mr. Pradeesh Kumar
who have given me the golden
opportunity to do this wonderful project
on the topic which also helped me in
doing a lot of Research and I came to
know about so many new things. I am
really
thankful
to
them.
Secondly I would also like to thank my
parents and friends who helped me a lot
in finalizing this project within the limited
time frame.
INDEX
 Introduction
 Aim
 Apparatus Required
 Theory
 Circuit Diagram
 Procedure
 Observations
 Result
 Precautions
 Sources of Error
Introduction
There are four basic factors of
inductor construction determining
the amount of inductance created.
These factors all indicate
inductance by affecting how much
magnetic field flux will develop for
a given amount of magnetic field
force (current through the
inductor’s wire coil.
The factors are:• NUMBER OF WIRE WRAPS, OR
“TURNS” IN THE COIL.
• COIL AREA.
• COIL LENGTH.
• CORE MATERIAL.
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 Required
A coil of large turns, A.C. source of
adjustable frequency, an electric
bulb, (6 V) A.C. ammeter of
suitable range, rheostat, a soft iron
rod, one way key, connecting wires
etc.
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
2
L =μ0μr N A
Where μr= Relative magnetic
permeability of magnetic material,
μ
μr = μ μ°
 N= Total number of turns in
solenoid
 A= Area of cross section of
solenoid
 l= Length of solenoid
Hence, the Self Inductance
depends upon
• No. of turns (N), L α N2
• Geometry of coil, L=A , L α
1/l
• Nature of core material, L= 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
I
E
=
rms
rms
Z
Where Z= (R2 + ω2L2)½=Impedance
of the A.C. Circuit
R= Resistance of bulb
L= Self Inductance of coil
ω = 2πf = Angular frequency
of A.C. source.
The brightness of bulb i.e. Heat
generated in bulb is
H=
2
I rmsZt
The brightness of bulb i.e. Heat
generated in bulb is
H= I2rmsZt
Or,
P=H/t= I2rmsZ
P= I2rms(R2 + ω2L2)½
Circuit Diagram
Procedure
 Make all connections as shown
in circuit diagram.
 Switch on the A.C. supply and
adjust the constant current in
the circuit by using the variable
resistor (R1) (let frequency of
source is 60 Hz and voltage is
6V).
 Record the current in A.C.
ammeter and see the brightness
of bulb.
 Now, put the soft iron rod inside
the inductor core and record the
current in A.C. ammeter and
again check the brightness of
bulb. The current and brightness
both decreases.
 Now, switch off the supply and
decrease the frequency of A.C.
source (say 50 Hz).
 Again switch on the supply and
adjust the current in circuit at
same constant voltage 6V by
using the rheostat. Note the
current in ammeter and
brightness of bulb. The current
and brightness both will
increases.
 Again insert the iron in the core
of coil and note the current and
brightness. The current and
brightness both decreases.
 Repeat the steps 5, 6 and 7 for
different frequency of A.C.
source (say 40 Hz,30 Hz and 20
Hz).
Fig 1.1: Experimental setup of experiment.
Observations
 Least Count Error= 0 A.
 Zero error of ammeter =0 A.
 Range of ammeter = 0-5 A.
S Frequency Current
No. of applied in
voltage(Hz) ammeter
without
iron rod
in coil
(A)
1. 60
2
2. 50
2.5
3. 40
2.9
4. 30
3.4
5. 20
4.1
Current
in
ammeter
with iron
rod in
coil (A)
1.8
2.3
2.6
3.25
4
Result
• The current in the circuit
decrease on inserting the iron
rod in the core of coil at
constant frequency of applied
voltage and brightness of bulb
decreases and vice-versa.
• The current in the circuit
increases on decreasing the
frequency of applied voltage
and vice-versa. Therefore, the
brightness of bulb increases.
Precautions
• The coil should have large
number of turns.
•
Current should be passed for a
small time to avoid the heating effect.
• There should not be parallax in
taking the reading of ammeter.
Sources of Error
• The resistance of circuit may
increases slightly due to heating
effect of current.
• There may be eddy current in
soft iron coil.
Bibliography
 https://www.google.com/url?sa=t&sourc
e=web&rct=j&url=https://en.wikipedia.org
/wiki/Inductance&ved=2ahUKEwj08Iniro7l
AhUJqI8KHTf0AnYQFjADegQIBBAB&usg=
AOvVaw2P7iDjtFkUuM4sVZ3Xvuee
 https://www.google.com/url?sa=t&sourc
e=web&rct=j&url=https://www.ukessays.c
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UJqI8KHTf0AnYQFjASegQIAxAB&usg=AO
vVaw101LPrKSTgDiDwgKYZPHV&cshid=15705968
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 https://www.google.com/url?sa=t&sourc
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