self inductance of coil

2015-16 of a Coil Factors effecting Self Inductance

Loyola High School, Patna of a Coil Factors effecting Self Inductance

ACKNOWLEDGEMENT

It would be my utmost pleasure to express my sincere thanks to My Physics Teacher Mr. Kundan Kr. Singh sir in providing a helping hand in this project. I would also like to thank Mr. Raju and our principal Bro. Satish K.Don without whom this project would have been not possible. Their valuable guidance, support and supervision all through this project is responsible for attaining this present form.

Siddhant Sah

XII-C

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Certificate This is to certify that, the project on the topic “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 in a circuit fed by an AC source of adjustable frequency.” has been sincerely and satisfactorily done by Siddhant Sah of Class XII C, Board Roll no. _______ , Loyola High School Patna, in partial fulfillment of Practical Examination for the session 2015-2016. I wish him success in his life. _____________________ Teacher in charge

________________________ Examiner’s signature

___________ principal

Experiment

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Aim:

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 in a circuit fed by an AC source of adjustable frequency.

Apparatus Required: I. II. III. IV. V. VI. VII. VIII.

A coil of large no. of turns, AC source of adjustable Frequency, An electric bulb, AC ammeter of suitable range, Rheostat, A soft iron Rod, One way key, Connecting wires

Theory: Self Inductance: It is a phenomenon where growth and decay of current is opposed due to change in magnetic flux between diff. layers of a coil, there is a self induced emf developed which opposes the source emf. ∂Ø α ∂I ∂t ∂t

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Or,

∂Ø = L ∂I , where L is a ∂t ∂t constant of proportionality called Coefficient of Self Inductance. From Laws of Electromagnetic Induction, E = -L ∂Ø ∂t Thus, self induction is Self Induced EMF developed due to rate of change of current. Suppose we have an Inductor(solenoid) of length ‘L’ having no of turns ’N’ connected to a source where current is 0 at t=0, then due to change of flux, a local emf is developed, Ø= L.I …..(1) Again, Ø=BNA, For a Solenoid, B= µoNI l Thus, Ø= Equating 1 and 2, 2

L=

µ0 N A l

µ 0 N 2 IA l

……. (2)

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Thus, co-efficient of self inductance is independent of current, but, depends on the no. of turns as well as length of solenoid.

Circuit Diagram:

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Procedure:  Made all the connections as shown in the circuit diagram.  Switched on the AC supply and adjusted the constant current in the circuit by using the rheostat.  Recorded the current in AC ammeter and checked the brightness of the bulb  The soft iron rod was put inside the inductor and the current passing through the ammeter was recorded. The current and Brightness both decreases.  Switched off the supply and decreased the frequency of the AC source.  Again switched on the supply and adjusted the current in the circuit at a constant voltage by using a rheostat. Noted the readings of the ammeter and checked the brightness of the bulb. The current and the brightness decreases.  Again inserted the iron rod in the core and noted the current and observed the brightness of the bulb. Both decrease.

Observations:

Loyola High School, Patna of a Coil Factors effecting Self Inductance

 LEAST COUNT OF AMMETER: 0.05A  RANGE OF AMMETER: 0 - 5A S.NO

1. 2. 3. 4. 5.

FREQUENCY APPLIED VOLTAGE

60 50 40 30 20

OF CURRENT AMMETER WITHOUT ROD

2 2.5 2.9 3.4 4.1

IN CURRENT AMMETER IRON IRON ROD

IN WITH

1.8 2.3 2.6 3.25 4

Result:  The current in the circuit decreases on inserting the iron rod in the core at constant frequency of applied voltage and brightness of bulb decreases and vice versa.  The current in the circuit increases on decreasing the frequency applied voltage and vice versa. Hence, the brightness of bulb increases.

Loyola High School, Patna of a Coil Factors effecting Self Inductance

Precautions: a. The coil should have large no. of turns. b. Current should be passed for a small time to avoid the heating effect.

Sources of Error:  The resistance

of

circuit

may

increase

slightly due to heating effect of current.  There may be eddy current in soft iron coil.

BIBLIOGRAPHY COMPREHENSIVE LABORATORY MANUAL OF Physics APC Publication

GRB PUBLICATION- PHYSICS CLASS XII

WEBSITES —

 www.icbse.com

Loyola High School, Patna of a Coil Factors effecting Self Inductance

 www.google.com  www.wikipedia.com