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AIM:To compare the E.M.Fs of two given primary cells using potentiometer.
APPARATUS: Potentiometer, a lechlanche cell,a daniel cell,an ammeter,a voltmeter,a galvanometer,a battery,a rheostat of low resistance,a resistance box,a one way key,a jockey,a set square,connecting wires and a piece of sand paper.
theory:(formula used) e1 = l1 e2 l2 where,E1 and E2 are e.m.f.s of two cells and L1 and L2 are the corresponding balancing lengths on potentiometer on wire.
PROCEDURE: 1. Draw a circuit diagram showing scheme of connections as in figure.
Remove the insulation from the ends of the connecting copper wires with a ssand paper. 3.Measure the e.m.f of the battery & the e.m.fs. of the cells. 4.Connect the positive pole of the battery to the zero end of the potentiometer & the negative pole through a one way key, an ammeter & a low resistance rheostat to the another end. 5. Connect the positive poles of the cells E1 & E2 to the terminal at the zero end and the 2.
negative poles to terminals a & b of the two-way key. 6. Connect the common terminal c of the two way key through a galvanometer & a resistance box to a jockey J. 7. Take maximum current from the battery making rheostat resistance zero.
8. Insert the plug to the one way key in the circuit & also in between terminals a & c of the two way key. 9. Take out a 2,000 ohms plug from the (R.B). 10. Press the jockey at the zero end & note the deflection in the galvanometer. 11.Slide the jockey gently over the potentiometer wires till you obtain a point where galvanometer shows no deflection. 12. Put the 2000 ohm plug back in R.B & obtain the null point position, using a set square. 13. Note the length l1 of the wire E1.Also note the current as indicated by the ammeter. 14. Disconnect cell E1 & connect the cell E2. 15. Repeat the same steps for E2 as its for E1.
16. Increase the current by adjusting the rheostat & obtain at least three sets of observations in a similar way. 17. Record your observations as given ahead.
RESULT: The ratio of E.M.fs, is_______
Precautions: 1. The connections should be neat & clean. 2.The plugs should be introduced in keys only when the observations are to be taken. 3.A low resistance rheostat should be used. 4.The jockey key should not be rubbed along the wire. It should touch the wire gently.
SOURCES OF ERROR: 1. The auxiliary battery may not be fully charged.
2.End resistance may not be zero. 3.The potentiometer wire may not be of uniform cross-section & materials density throughout its length.
EXPEREIMENT - 2
AIM: To determine the internal resistance of a given primary cell using potentiometer.
A potentiometer, a battery,two
one-way keys, a rheostat of low resistance, a galvanometer, a high resistance box, a fractional resistance box, an ammeter, a voltmeter, a cell, a jockey, a set square, connecting wires & a piece of sand paper.
THEORY: (Formula Used ) The internal resistance of the cell is given by, r=l1 – l .R l
where l1 & l are the balancing lengths without shunt and with shunt, respectively, & R is the shunt resistance in parallel with the given cell.
PROCEDURE: 1. Clean the ends of the connecting wires with sand paper & make tight connections according to the circuit diagram. 2. Tight the plug of the resistance box. see that e.m.f. of the battery is more than that of the given cell, otherwise nullpoint will not be obtained. 4. Take maximum current from the battery, making rheostat resistance zero. 5. Without inserting the plug in the key K 2 adjust the rheostat such that the null
point is obtained on the 4 th wire of potentiometer. 6. Insert the 2000 ohm plug back in its position in resistance box & by slightly adjusting the jockey near the previously obtained position of full null point, obtain null point position, using set square. 7.Measure the balancing length l1 from end P. 8. Slide the jockey along the potentiometer wire & obtain null point. 9. Insert 2000 ohm plug back in its position in R.B & if necessary make further adjustment for sharp null point. 10.Measure the balancing length l2 from end P. 11.Remove the plug keys at K1 & k2. Wait for sometime & for the same value of current, repeat above steps.
12. Repeat the observations for different values of R repeating each observation twice. 13. Record your observations as given below.
Result: The internal resistance of the given cell is_______
Precaution: 1.The e.m.f. should be greater than that of the cell. 2.Cell should not be distributed during experiment. 3.Jockey should not be rubbed against the potentiometer wire.
Sources of error: Same as of previous experiment.
ALL INDIA SENIOR SECONDARY CERTIFICATE EXAMINATION A PROJECT REPORT SUBMITTED TO CHEMISTRY DEPARTMENT ADITYA BIRLA PUBLIC SCHOOL KOVAYA,
BY:- SHANTANU CHAUHAN ROLL NO: XII SCI. 2010-2011 PRINCIPAL
CERTIFICATE This is to certify that this project work is submitted by SHANTANU CHAUHAN to the Physics department, Aditya Birla Public School, Kovaya was carried out by her under the guidance & supervision during academic year 20102011.
Principal Aditya Birla Public School
Shri.Chaturvedi (Head of physics dept.) Kovaya
ACKNOWLEDGEMENT I wish to express my deep gratitude and sincere thanks to Principal, Raji Jayaprasad, Aditya Birla public school, kovaya for her encouragement and for all the facilities that she provided for this project work. I sincerely appreciate this magnanimity by taking me into her fold for which I shall remain indebted to her. I extend my hearty thanks to Shri CHATURVEDI physics teacher, who guided me to the successful completion of this project.I take this opportunity to express my deep sense of
encouragement,constructive comments, sympathetic attitude and immense motivation, which has sustained my efforts at all stages of this project work. I can’t forget to offer my sincere thanks to Shri. Pankaj Bajpai & my classmates who helped me to carry out this project work successfully & for their valuable advice & support, which I received from them time to time.
I do hereby declare that this project work has been originally carried under the guidance and supervision
physics department, Aditya Birla Public School, kovaya.
DEDICATION I DEDICATE THIS PROJECT WORK TO THE LOTUS FEET OF
Shri. N.K. PATEL & MY MOTHER
Smt. NEETA PATEL
PHYSICS (Part 1& 2) – Textbook for Class XII; National Council of Educational Research and Training.
Comprehensive Practical PHYSICS for Class XII; Laxmi Publications.