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An Experiment To Find the Resistivity of a Wire

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Introduction

3

AN EXPERIMENT TO FIND THE RESISTIVITY OF A WIRE

In this experiment, I am going to find out the relationship between Resistivity, Resisistance, cross sectional area and length of the wire, which in this case is Constantan. So I can find the Resisitivity of Constantan.

RESISTIVITY of a wire is the property of the wire, measured in ohmmeter. It is a measure of how the material opposes the flow of current through it. The Resistivity of a wire along with its Resistance is temperature dependent.

To do this, I will find out the resistance of the wire at different length by measuring the potential difference over a range of 0.05v-0.80v and the current at that particular length of wire, to find the relationship between Resistance and length.

There are several factors that may affect the Resistance of a wire. Some of which are:

• The material of the wire
• The cross sectional area
• The length of the wire
• The temperature of the wire.

In doing this, I have to keep the material of the wire constant by using the same type of wire which in this case is Constantan, the cross sectional area of the wire will be kept constant

Middle

0.03

1.67

0.10

0.06

0.15

0.09

0.20

0.12

0.25

0.15

0.30

0.18

0.15

0.05

0.02

2.50

0.10

0.04

0.15

0.06

0.20

0.08

0.25

0.10

0.30

0.12

0.20

0.05

0.02

3.33

0.10

0.03

0.15

0.04

0.20

0.06

0.25

0.07

0.30

0.09

0.25

0.05

0.01

4.17

0.10

0.02

0.15

0.03

0.20

0.05

0.25

0.06

0.30

0.07

0.30

0.05

0.01

5.00

0.10

0.02

0.15

0.03

0.20

0.04

0.25

0.05

0.30

0.06

Table of results I got when I varied the Cross Sectional Area using a wire of length 0.10m

 Cross Sectional Area / Χ10-8

Conclusion

I feel that the only way to make my results more accurate would be to use a different method. I could even use a rheostat in place of a wire, because it is essentially a long coiled wire that is connected at different lengths to change the Resistance of the wire. If I were to do this experiment again, I will measure the diameter of the wire at 3 different positions on the wire and take the average of the 3 values. And I will use a Digital Voltmeter and Ammeter and take a wider range of readings like about 8 readings to ensure a greater accuracy in the obtained results and in the plotted graphs. I will then repeat this experiment twice for each potential difference and current readings in a particular length of wire.

The value for the Resistivity of constantan I found is 2.56 × 10-7 Ωm. This is different from the value of Resistivity in the Data book which is 4.70 Χ 10-7Ωm, with an error of  45%. This error may have been as a result of what I talked about in my evaluation. It may also have been as a result of the different method used in obtaining this result.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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