PHYSICS

INVESTEGATORY
PROJECT
OHMS LAW
SUBMITTED BY:

STUDENT NAME HALL TICKET NUMBER

DEPARTMENT OF PHYSICS

SRI CHAITANYA TECHNO SCHOOL

Kothanur Dinne Main Road, Near Bus Stop 8th Phase, JP Nagar,
Jumbo Sawari, Dinne, Bengaluru, Karnataka 560078
 CERTIFICATE
This is to certify that the Project / Dissertation entitled Ohms
Law Physics investigatory project is a bonafide work done by
Mr. / Ms. …………………..................…..of class XII in partial fulfillment
of CBSE’s AISSCE Examination 2024-25 and has been carried
out under my direct supervision and guidance. This report or a
similar report on the topic has not been submitted for any
other examination and does not form a part of any other course
undergone by the candidate.

Signature of Student Signature of Teacher/Guide

Name : ……………………. Name : ........................
Roll No.: ……………………. Designation: ........................

Signature of Principal
Name:
Place: JP Nagar

Date:……………..
 ACKNOWLEDGEMENT
I would like thank the institution for giving the
opportunity to encase and display our talent through
this project.
I would like to thank my physics teacher
............................................................. for having the
patience to guide me at every step in the project
I am also grateful to the CBSE BOARD for challenging
and giving us this project in which we all were so
engrossed.
I would also like to thank my parents and friends who
helped me in getting the right information for this
project.
TABLE OF CONTENTS
1)Introduction

2)Ohms Law equation

3)Relationship between voltage current and resistance

4)Experimental verification of ohms law

5)Apparatus Required

6)Procedure

7)Observation

8)Calculation

9)Result

10)Precautions

11)Bibliography
 INTRODUCTION

Resistance
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.

i=v/r

Where, I is the current through a conductor in units of amperes, V is the

potential difference measured across the conductor in units of volts, and
& R is the resistance of the conductor in units of ohm's. More specifically,
Ohm's law states that the R in this relation is constant, independent of the
current
The electrical resistance of an electrical conductor is the opposition to
the passage of an electric current through that conductor. The inverse
quantity is electrical conductance, the ease with which an electric current
passes. Electrical resistance shares some conceptual parallels with the
notion of mechanical friction. The SI unit of electrical resistance is the
ohm, while electrical conductance is measured in siemens (S).

An object of uniform cross section has a resistance proportional to its

resistivity and length and inversely proportional to it's cross-sectional
area. All materials show some resistance, except for superconductors,
which have a resistance of zero.
 Resistivity
The resistance of a given wire depends primarily on two factors: What
material it is made of, and it's shape. For a given material, the resistance is
inversely proportional to the cross- sectional area; for example, a thick
copper wire has lower resistance than an otherwise identical thin copper
wire. Also, for a given material, the resistance is proportional to the length;
for example, a long copper wire has higher resistance than an otherwise -
identical short copper wire. The resistance R of a conductor of uniform
cross-section, therefore, can be computed as:

R=1/A

where, "L" is the length of the conductor, measured in meter(m), “A”is the
cross- sectional area of the conductor measured in m², "o" is the electrical
resistivity (also called specific resistance) of the material, measured in Ω-
m. The resistivity is the proportionality constant, and therefore depends
only on the material of the wire, not the geometry of the wire. Resistivity
and Conductivity are reciprocals:

ρ=1/σ

* Resistivity is measure of the material's ability to oppose electric current

The resistivity of different materials varies by an enormous amount:

For example, the conductivity of Teflon is about 1030 times lower than
the conductivity of copper. Why is there such a difference? Loosely
speaking, a metal has large no. of "delocalized" electrons that are not
stuck in any one place, but free to move across large distances, whereas in
an insulator (like Teflon), each electron is tightly bound to a single
molecule, and a great force is required to pull it away. Semiconductors lie
between these two extremes. Resistivity varies with temperature. In
semiconductors, resistivity also changes when exposed to light.

.
AIM: To find the resistivity of wires of different metals using OHM'S LAW.

APPARATUS: 5 wires of different metals and respective lengths.

A battery eliminator

d.c. Voltmeter (range 3V)

d.c. Ammeter (range about 500mA)

A rheostat

One plug key

Thick connecting wires

Sand paper
PROCEDURE: Arrange the various components of the circuit
accordingly with plug out of one-way key.

Rub the ends of the connecting wires with a sand

paper to remove any oxidized insulating coating.
Study the circuit carefully and make tight
connections accordingly using thick connecting
wires.

Ensure that the ammeter is connected in series with

the resistance wire with it's positive terminal
towards the positive of the battery. Also ensure
that the voltmeter is connected in parallel to
resistance coil R in such manner that the current
enters at it's positive end.

Connect rheostat such that one of its lower

terminals and the upper terminals are used.

Insert the plug in key K.

Adjust the rheostat so that small current flows

through the circuit. Record the readings of the
ammeter and the voltmeter.

Shift the rheostat contact to shift the current and

take the readings again.

Cut the resistance wire at the ends just coming out

of voltmeter. Stretch it along the meter scale and
measure it's length 1.

Record your observations.

OBSERVATION TABLE:

IRON WIRE

CURRENT VOLTAGE RESISTANCE

150mA 0.20V 1.3 ohm

200mA 0.25V 1.001 ohm

300mA 0.30V 1 ohm

OBSERVATION TABLE:

ALUMINIUM WIRE

CURRENT VOLTAGE RESISTANCE

150mA 0.20V ohm

200mA 0.25V 0.66 ohm

300mA 0.30V 0.75 ohm

OBSERVATION TABLE:

MAGANIM WIRE

CURRENT VOLTAGE RESISTANCE

150mA 0.20V 1.3 ohm

200mA 0.30V 1.5 ohm

300mA 0.40V 1.3 ohm

OBSERVATION TABLE:

COPPER WIRE

CURRENT VOLTAGE RESISTANCE

150mA 0.10V 0.5 ohm

200mA 0.20V 0.54 ohm

300mA 0.30V 0.6 ohm

CALCUALTIONS:

IRON WIRE

Length of wire= 21cm

Thickness= 0.54×10^-2m

Area= 0.22 ×10^-6 m²

mean resistance= (1.3+1.001+1)/3= 1.1 Ω

resistivity= RA/L= 10.5×10^-8 Ωm

ALUMINIUM WIRE

Length of wire= 68cm

Thickness=0.66×10^-2m

Area=0.28×10^-6m²

Mean Resistance=(0.5+0.66+0.75)/3=0.630

Resistivity= RA/L= 2.7×10^-8 Ωm

MAGANIM WIRE

Length of wire=57cm

Thickness = 0.66 * 10 ^ - 2

Area=0.19×10^-6m²

Mean Resistance = (1.3 + 1.5 + 1.3) / 3 = 1.36Omega

Resistivity= RA/L=48.2×10^-80m

COPPER WIRE

Length of wire=42cm

Thickness = 0.49 * 10 ^ - 2 * m

Area=0.7703×10^-6m²

Mean resistance e = (0.5 + 0.54 + 0.6) / 3 = 0.54Omega

Resistivity= RA/L= 1.7×10^-8 Ωm

RESULT: The resistivity of wires are:

1) For iron wire- 10.5 * 10 ^ - 8 ohm m

2) For aluminium wire- 2.7 * 10 ^ - 8 ohm m

3) For manganim wire- 48.2 * 10 ^ - 8 ohm m

4) For copper wire- 1.7 * 10 ^ - 8 ohm m

PRECAUTIONS: Connections should be tight.

Short circuiting should be avoided.

The plug should be inserted only while taking

observations otherwise current would cause
unnecessary heating in this current.
CONCLUSION:
Ohm's law, in the form above, is an extremely useful
equation in the field of electrical/electronic
engineering because it describes how voltage, current
and resistance are interrelated on a "macroscopic"
level, that is commonly, as circuit elements in an
electrical circuit. Physicist who study the electrical
properties of matter at the microscopic level use a
closely related and more general vector equation,
sometimes also referred to as OHM'S law, having
variables that are closely related to the V, I and R
scalar variables of Ohm's law, but which are each
functions of positions within the conductor. Physicists
often use this continuum form of Ohm's law-

E-PJ where "E" is the electric field vector with units of

volt /meter, "J" is the current density vector with units
of amperes/unit area, and "p" is the resistivity with
units of Q-m. The above equations is sometimes
written as J=0E where "σ" is the conductivity which is
reciprocal of "p".
BIBLIOGRAPHY:
www.google.com

www.youtube.com

https://mycbseguide.com

https://en.wikipedia.org