Self Inductance 3

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.
ACKNOWLEDGEMENT
I would like to express my special thanks of

gratitude to my teacher Mr. HIMANSHU
GUPTA and our principal ma’am Mrs.
RICHA VASHISHTH 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
1. Introduction
2. Aim
3. Apparatus Required
4. Theory
5. Circuit Diagram
6. Procedure
7. Observations
8. Result
9. Precautions
10. Sources of Error
Don’t share
with anyone
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
L =μ0μr N2 A
Where μr= Relative magnetic

permeability of magnetic material,
μr = μμμ°
 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 rms=E 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= I2rmsZt
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 No. Frequency of Current in Current in

applied ammeter ammeter with
voltage(Hz) without iron iron rod in coil
rod in coil (A) (A)
1. 60 2 1.8
2. 50 2.5 2.3
3. 40 2.9 2.6
4. 30 3.4 3.25
5. 20 4.1 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.

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Factors on which self inductance of coil

To study the factors on which the Self Inductance of a coil

I would like to express my special thanks of

There are four basic factors of inductor construction

The factors are:-

• NUMBER OF WIRE WRAPS, OR “TURNS” IN THE

To study the factor on which the Self

A coil of large turns, A.C. source of

Self Inductance is the property of a coil

Where μr= Relative magnetic

S No. Frequency of Current in Current in

• The current in the circuit increases on decreasing the

• The resistance of circuit may

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