INSTITUTION NAME: DEDAN KIMATHI UNIVERSITY OF TECHNOLOGY

NAME: PETER MUIGAI NG’ANG’A

REGISTRATION NUMBER: E021-01-1221/2022

SIGNATURE: -------------------------------------------

DEPARTMENT: ELECTRICAL AND ELECTRONIC ENGINEERING

COURSE: B.Sc. ELECTRICAL AND ELECTRONIC ENGINEERING

UNIT NAME: WORKSHOP PRACTICE II

UNIT CODE: EEE 2103

TITLE OF THE REPORT: RESISITIVITY OF DIFFERENT MATERIALS

LECTURER’S NAME: MR. ELIAS MBUTHIA

EXPERIMENT DATE: 15th JUNE,2023

SUBMISSION DATE: 22th JUNE,2023 

AIMS AND OBJECTIVES

The main objective of carrying the experiment out is to determine the resistivity of a known wire of
known material and to study the relationship of resistance with area of cross-section and the length.

It was also to determine the influence of material type on the resistivity.

INTRODUCTION

Resistivity is the ability of a material to behave as a resistor. The resistance of a material is dependent on
a number of factors such as temperature, cross-section area and length. The relationship between
resistance length and cross-section area gives the resistivity of a material.

THEORY

Ohm’s law describes the relationship between the resistance R of a wire, the voltage drop across it, V,
and the current through the wire, I. This is formally given by

R = V/I

The resistance of the wire is a function of both geometry of the wire and the material that the wire is
made of.

For a given wire of fixed length, the electric current passes easily through the larger area of cross section
as compare to the smaller area of cross-section. Hence, the relationship between the crosssectional area
(A) and electrical resistance (R) can be written as

1
Rα
A

But for given wire with fixed area of cross-section, the wire of longer length (l) will have more electric
resistance as compared to the wire of shorter length and their relationship can be written as:

𝑅 ∝ 𝑙.

But,

L
R=ρ A

Where ρ is proportionality constant and is known as the resistivity. Resistivity is material specific and is
defined as the resistance of a wire of unit length and unit cross-section area. Its SI unit is Ω.m
TOOLS AND ACCESSORIES

TOOLS

Pliers.

Steel rule

ACCESSORIES

Multi-meter.

PROCEDURES

1. The copper wires were stripped.

2. The meter rule was placed horizontally on the bench with the wire facing up.
3. The diameter of the four different wires provided was determined and recorded in a table.
4. The area of cross-section of the wires was determined.
5. The cables were connected to the multi-meter to measure the resistance one end of black cable
to common point and one end of red cable to the point with symbol Ω.
6. The second end of the black cables was fixed to one end of the wire.
7. The multi-meter was turned on and the resistance button pressed.
8. The second end of the cable was placed exactly 10 cm from the other end and the resistance
recorded.
9. The procedure was repeated for 10 cm increment to 100 and the resistances were recorded in
the table.

DATA PRESENTATION

Aluminum wire

l(m) D1(m) A1(m2) R1(Ω) Slope(Ω/m) Resistivity

0.1 3.81*10-3 1140*10-6 5.15 0.00567 6.464*10-8

0.2 5.90

0.3 6.50

0.4 7.35

0.5 7.60

0.6 8.25

0.7 8.60
 0.8 8.82

7 strand copper wire

l(m) D1(m) A1(m2) R1(Ω) Slope(Ω/m) Resistivity

0.1 1.37*10-3 1.474*10-6 9.90 0.00333 4.913*10-8

0.2 10.15

0.3 10.95

0.4 11.35

0.5 11.78

0.6 11.95

0.7 12.63

0.8 12.90

Nichrome wire

l(m) D1(m) A1(m2) R1(Ω) Slope(Ω/m) Resistivity

0.1 2.93*10-3 6.473*10-6 13.85 0.003215 2.081*10-8

0.2 14.05

0.3 14.15

0.4 14.60

0.5 14.80

0.6 14.90

0.7 14.90
0.8 14.98

Single strand wire

l(m) D1(m) A1(m2) R1(Ω) Slope(Ω/m) Resistivity

0.1 0.47*10-3 0.1735*10-6 11.45 0.005 4.913*10-8

0.2 12.15

0.3 13.40

0.4 13.45

0.5 13.50

0.6 13.5

0.7 14.3

0.8 15.5
 18 A Graph of resistance against the length for four different wires

16

14

12

10
Resistance

6
Aluminum wire

4 7 strand copper wire

single strand copper wire

2
Nichrome wire

0
1 2 3 4 5 6 7 8
Length

Slope= Y2-Y1/X1-X2

Slope for aluminum=0.00567

Slope for single strand copper wire=0.005

Slope for 7 strand copper wire = 0.00333

Slope for nichrome wire = 0.003215

DISCUSSION AND DIAGRAMS

The experiment is carried out using a multimeter by determining the resistance of the wires at different
lengths by increasing the length step by step. A graph of resistance against resistance is then used to
determine the resistivity of the wires by determining the slope of the graph and then multiplying it with
the area.

The resistance is directly proportional to length and area is inversely proportional to resistance.

From the experiment, the factors affecting resistance of a material are; type of material, cross-section
area and length of a material.

The 7- strand copper wire has a lower resistance compared to the single strand because cross-section
area is inversely proportional to resistance thus since the 7-strand wire has a larger cross-section area
the resistance is lower.

The graph is of straight lines because resistance is directly proportional to the length.
RESULTS AND OBSERVATIONS

It was observed that the graphs were of straight line and that the resistance decreased with increase in
cross-section area. The values of the resistances also varied with different materials thus the factors
affecting the resistance were determined.

SOURCES OF ERRORS

Errors in determining the diameter of the different wires due to zero error of the micrometer screw
gauge.

Errors in reading the resistance from the multimeter

RECCOMMENDATIONS

Ensure that the zero error is added or subtracted from the reading made.

Ensure that the multi-meter reading is made correctly.

CONCLUSION

The factors influencing the resistance of a material were understood and the concept of resistance was
differentiated from resistivity. Learners were able to learn how to determine the resistivity by
formulating from the concepts taught.
REFERENCES

Material Science Lab Manual.

https://www.docsity.com/en/resistivity-lab-report/7448088/

https://academics.uccs.edu/rtirado/PES_2160_Lab/Pes_2160_Lab6.pdf