JAWAHAR HIGHER SECONDARY SCHOOL

NEYVELI(AFFLIATED TO C.B.S.E)

SESSION : 2014-2015

PHYSICS- INVESTIGATORY PROJECTON

Study on validity of Seebeck Effect for copper-aluminium themocouple

“Intelligence plus character - that is the goal of true education.”

SUBMITTED TO

MR.K.VIJAYA KUMAR

CLASS 12 PHYSICS TEACHER

SUBMITTED BYN.R.ARUN KAUSHIK

C.BATHRINATH

S.BALAJIR.M.LALIT KUMAR

CERTIFICATE

This is to certify that the project

work titled “Study on validity of SEEBECK

EFFECT for copper aluminium thermocouple”

submitted by N.R.ARUN

KAUSHIK/C.BATHRINATH/S.BALAJI/ R.M.LALIT

KUMAR (class XIIth –Section A - PCM group)

in partial fulfilment of the credit for the

physics project evaluation from “JAWAHAR

HIGHER SECONDARY SCHOOL, NEYVELI” , is

the bonafide work of the student done under

the guidance and supervision of

Mr.K.VIJAYAKUMAR , Physics Teacher,JHSS

during session 2014-2015, as a project

report.

NAME: SUBJECT:

REGISTRATION NO. : CLASS:

DATE: PLACE:

INTERNAL EXAMINER EXTERNAL EXAMINER

PRINCIPAL

ACKNOWLEDGEMENTAcknowledgement is the most beautiful page in any project’s

final pages. More than a formality, this appears to us the best

opportunity to express our gratitude.

Our project can never begin without you, dear GOD. Rather than saying “thank you” to you, you know that we feel like saying ‘I love you’, to you, always. We must say thanks to our parents who provided us sufficient money and help in making of this project.

Mr.K.Vijaya Kumar, you are the real foundation of the project done by us. Our project would never have been possible without your guidance. Thank you very much. Special thanks to our Principal, our Vice Principal and our physics teachers, Mr. B.Soma Sankara Rao and Mrs. V.Vijayalakshmi who gave support to us and library which provides all useful books related to this project.

Next on our thank list are our friends, teachers who really showered constructive feedbacks and suggestions without which this

project would not have been in present form.

N.R.ARUN KAUSHIK

R.M.LALIT KUMAR

C.BATHRINATH

S.BALAJI

DECLARATION

We hereby declare that the project work entitled

“Study on validity of SEEBECK EFFECT for copper aluminium thermocouple” submitted to the “JAWAHAR HIGHER SECONDARY SCHOOL, NEYVELI” is a record of original work done by us, except for quotations and summaries which have been duly acknowledged, under the guidance of

"Mr. K.Vijaya Kumar, Physics Teacher, JHSS ". The project has not been accepted for any credits based on investigatory projects previously. N. R. ARUN KAUSHIK

C.BATHRINATH

R.M.LALIT KUMAR

S. BALAJI

INDEXSL. TOPIC PAGE

NO

. NO.

1 OBJECTIVE  1

 2 INTRODUCTION  2

 3 AIM  5

 4 APPARATUS REQUIRED  6

 5 THEORY  7

 6 PROCEDURE  9

 7 OBSERVATION & CONCLUSIONS  10

 8 BIBLIOGRAPHY  11

OBJECTIVE

The objective of this

project is to experimentally verify the SEEBECK

EFFECT on a thermo couple.

INTRODUCTION

SEEBECK EFFECT FOR Cu-Al COUPLE 

   

HISTORY

The  Seebeck effect is the conversion of  temperature differences

directly into electricity and is named after the Baltic

German physicist Thomas Johann Seebeck.

Seebeck, in 1821, discovered that a compass needle would be

deflected by a closed loop formed by two different metals joined in two

places, with a temperature difference between the junctions. This was

because the metals responded to the temperature difference in

different ways, creating a current loop and a magnetic field.

Seebeck did not recognize there was an electric current involved, so

he called the phenomenon as thermomagnetic effect. Danish physicist 

Hans Christian Øersted rectified the mistake and coined the term

"thermoelectricity".

The Seebeck effect is a classic example of an electromotive force (emf)

and leads to measurable currents or voltages in the same way as any

other emf. Electromotive forces modify Ohm's law by generating

currents even in the absence of voltage differences (or vice versa)

Seebeck EFFECT

The Figure shows two metallic strips, made of different metals and joined at the ends to form a loop. If the junctions are kept at different temperatures, there is an electric current in the loop.The magnitude and the direction of the emf depend on the metals and the temperatures of the hot and cold junctions.

Such a combination of two metals is called a thermocouple. The following graph shows the free energy variations of a thermocouple in Seebeck experiment.

EXPLANATION FOR Seebeck EFFECT

The production of Seebeck emf can be explained as under: All metals contain large number of free electrons. The density of free electrons is different in different metals and depends upon the temperature. When two different metals are connected to form two junctions and these junctions are kept at different temperatures free electrons will diffuse into one another metal at the junctions.

Net flow is from higher electron pressure to the metal of lower electron pressure. If the junctions are at the same temperature the emf at one junction will be equeal and opposite to that in the other junction. Hence the emf is zero.

Thermoelectric Series.

For given temperatures of hot and cold junctions, the direction of the current in a thermocouple depends on the metals chosen. Metals are arranged in a particular sequence which may be used to predict the direction of the current in the temperature range 0’ C to 100’C. This sequence known as the thermoelectric series, is as follows:

Antimony, nichrome, iron , zinc, copper, gold, silver, lead, alumi9nium, mercury, platinum-rhodium, platinum, nickel, constantan, bismuth.

At the cold junction, the current is from the metal coming earlier in the series to the metal coming latter in the series. For example, in a copper-aluminium thermocouple, the current will be from aluminium to copper at the cold junction.

Also, the series gives an idea of the relative magnitude of emf for different thermocouples, Farther apart two metals lie in the series, larger is the emf produced.

AIM

The aim of this project is to study the generation of thermo-current for Cu-Al (copper-aluminium) thermocouple.

APPARATUS REQUIRED

THEORY

COPPER AND ALUMINIUM WIRES

MULTIMETER

CANDLE STICKS

ICE CUBES THERMALLY INSULATED LABORATORY

Let us consider a thermocouple of two metals Fe and Cu. Their junctions are kept cold and hot. If a galvanometer G is connected in the circuit the galvanometer deflection is observed which corresponds to thermoelectric current. If the temperature of the hot junction be continuously increased, thermoelectric current increases until maximum value is reached. The temperature of the hot junction at which maximum current flows is constant for a given thermocouple. It is independent of the temperature of cold junction and is called the neutral temparture, for the couple. On further increasing the temperature of hot junction the current decreases to zero and is then reversed. The temperature at which the current is zero and its reversal begins is called

inversion temperature. It depends on the temperature of cold junction and the chosen couple. It is always as much above the neutral temperature as the cold junction is below it. Thus

Ti – Tn =Tn –Tc

Here, Ti = inversion temperature Tn = neutral temperature and Tc = cold junction temperature.

The graph between the emf and the temperature difference of the two junction is of the parabolic form of majority of couples. Thus, emf can be given as,

e = a + bt + ct²

PROCEDURE:

Take two copper wires AB and CD and an aluminium wire EF.

Connect the wires AB and CD though a multimeter.

The ends A and D are tied with the ends E and F of aluminium wire.

The tied wires are kept in hot and cold junction. Candles and Ice cubes act as heat source, heat sink respectively.

Now the multimeter shows deflection.

OBSERVATION AND

CONCLUSIONS

From the experiment, we observe that a milli-volt potential difference was created between the hot and cold junctions. So there was a small current flowing through the thermocouple(measured through a sensitive multimeter). Like this, there are quite a few thermocouples which can show Seebeck effect. Thus we have experimentally verified and validated the Seebeck effect.

BIBLIOGRAPHY

Reference books:

NCERT CLASS 12 PHYSICS BOOKS - PART I, II

CONCEPTS OF PHYSICS -BY H.C.VERMA

NCERT LABORATORY MANUAL - CLASS 12 PHYSICS

UNDERSTANDING PHYSICS- BY D.C.PANDEY

Reference websites:

www.google.co.in en.wikipedia.org