Dependence of current on pd across a resistor

1. DEPENDENCE OF
CURRENT ON PD ACROSS
A RESISTOR
DONE BY:
ANJALI
XII-A

2. ACKNOWLEDGEMEN
T
I express my sincere gratitude to Shri.A.P Vinod
Kumar, Principal, Kendriya Vidyalaya Ottapalam who
provided me with all arrangements to carry out my
project.
I would like to thank my Physics teacher
Smt.Beenakumari, who has helped me to complete
this project successfully by providing the necessary
assistance and constructive suggestions for the
improvement of all aspects related to this project.
I also owe a great deal of thanks to my parents who
always boosted up my morale and encouraged me to
carry on this project.
I am also thankful to my friends for helping me in
completion of my project and sharing with me their
views about the project.

3. CONTENTS
1) Acknowledgement
2) Introduction
3) Objective
4) Requirements
5) Theory
6) Procedure
7) Observations
8) Calculations
9) Result
10) Precaution
11) Bibliography

4. INTRODUCTION
Ohm's law states that the current through a conductor between
two points is directly proportional to the potential difference across the
two points. Introducing the constant of proportionality,
the resistance, one arrives at the usual mathematical equation that
describes this relationship:
,
Where
• ‘I’ is the current through the conductor in units of amperes,
• ‘V’ is the potential difference measured across the conductor in
units of volts
• ‘R’ is the resistance of the conductor in units of ohms.
R depends upon the material, temperature and dimensions of the
conductor.
The law was named after the German physicist Ohm. The above
equation is the modern form of Ohm's law.
VECTOR FORM OF OHM’S LAW
Where
V=I/R
E=J σ

5. • ‘J’ is the current density at a given location in a resistive material,
• ‘E’ is the electric field at that location
• ‘σ’is a material-dependent parameter called the conductivity.
This reformulation of Ohm's law is due to Gustav Kirchhoff
OBJECTIVE
• To study the dependence of current (I) on the
potential difference (V) across a resistor and
determine its resistance.
• Also plot a graph between V and I
REQUIREMENTS
• An unknown resistance coil or a resistance wire
• A voltmeter
• An ammeter
• A battery
• A rheostat
• Connecting wires

6. • A piece of sand paper
THEORY
If I be the current flowing through a conductor and V be the
potential difference across its ends, then according to Ohm's Law,
CIRCUIT DIAGRAM
GRAPH: If we plot voltage on the y-axis of a graph and current
on the x-axis of the graph, we will get a straight-line. The gradient

7. of the straight-line graph is related to the resistance of the
conductor.
PROCEDURE
• Arrange the apparatus as per the circuit diagram
• Clean the ends of the connecting wires with sand
paper to remove insulation and make them shiny.
• Make neat, clean and tight connections according to
the circuit diagrams. Take care to connect the
ammeter and the voltmeter with their correct polarity.
(+ve to +ve, -ve to –ve)
• Determine the least count of voltmeter and ammeter,
and also note the zero error, if any.
• Insert the key K and slide the rheostat contact to see
whether the ammeter and voltmeter are showing
deflections properly.
• Adjust the sliding contact of the rheostat to get a
small deflection in ammeter and voltmeter.
• Record the readings of the ammeter and voltmeter.

8. • Take at least 6 sets of readings by adjusting the
rheostat gradually.
• Plot a graph with V along Y axis and I along X axis.
(The graph will be a straight line)
• Determine the slope of the V-I graph which gives the
resistance of the wire.
OBSERVATIONS
1. Length:
Length of the resistance wire l =......cm
2. Range:
Range of the given ammeter = .......A.
Range of the given voltmeter = .......V.
3. Least count:
Least count of ammeter = .......A.
Least count of voltmeter = .......V.
4. Zero error:
Zero error in ammeter, e1 = .......A.
Zero error in voltmeter,e2 = ......V.

9. 5. Zero correction:
Zero correction for ammeter, (-e1) = .......A.
Zero correction for voltmeter, (-e2) = ......V.
OBSERVATION TABLE
CALCULATIONS
S.No: Material V I
1 Copper
2 Nichrome

10.  R from graph = slope = 1: For copper =
2: For nichrome =
GRAPHS
S.No: Material V/I=R Mean Value
1 Copper
2 Nichrome

11. RESULT

12. • Ohm’s law is verified as the I v/s V graph is a
straight line.
• The resistance of the given wires :
COPPER =
NICHROME =
PRECAUTIONS
• All the electrical connections must be neat and
tight.
• Voltmeter and ammeter must be of proper range.
• The key should be inserted only while taking
readings.

13. BIBLIOGRAPHY
• www.wikipedia.org
• www.onlinelabs.com