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I am going to examine the resistance of a length of wire.

Extracts from this document...

Introduction

W. Vaughan                27/04/2007

PHYSICS COURSEWORK

INVESTIGATING THE RESISTANCE OF A WIRE

INTRODUCTION

I am going to examine the resistance of a length of wire. There are a number of variables which I think will alter the behaviour of the resistance. These are heat, length, diameter, atmospheric pressure and height. There are two that are feasible to investigate in classrooms which are length and diameter. From these two I have decided to choose length as there seems to be a wider range of variables compared to the diameter of a wire. To check that this variable showed significant variation I carried out a preliminary experiment to verify this. From this preliminary experiment I observed that there definitely seemed a correlation between the length of the wire and the resistance achieved. I will define the quantities in Ω (ohms).

HYPOTHESIS

I predict that if we double the length of the wire the resistance will double therefore showing a direct correlation between the two. I compiled these results from the quick preliminary experiment.

EXPLANATION

Resistance is the property that transforms electrical energy into heat energy. All the atoms in conductors have free electrons. When there is a potential difference through the metal all the electrons line up creating an electrical current. Resistance is encountered when these electrons collide with other fixed particles in the material.

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Middle

Length (m)

Voltage (V)

Amperes (I)

Resistance (Ω)

2 Decimal Places (Ω)

0.2

1.71

1.564

1.093350384

1.09

0.4

1.89

0.759

2.490118577

2.49

0.5

1.91

0.594

3.215488215

3.22

0.6

1.93

0.49

3.93877551

3.94

0.8

1.96

0.347

5.648414986

5.65

1

1.97

0.285

6.912280702

6.91

1.5

2.01

0.212

9.481132075

9.48


2nd Attempt

Length (m)

Voltage (V)

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Conclusion

To improve the accuracy of the experiment an extra person would have helped enormously especially the in preparing of the wire and obtaining the desired length. Also using a more precise voltmeter and ammeter in the experiment would have improved the accuracy of the readings. A rheostat (this is a device to vary the amount of a current passing through it to complete a circuit2) could also be used to minimise errors when preparing a length of wire about to be tested. I would also try and regulate the temperature as this can affect the resistance of the wire.

In my introduction I mentioned the following variables heat, length, diameter, atmospheric pressure and height. I have investigated how length affects the resistance and if I had more time I would then go on to investigate the effects of diameter on the resistance of a fixed length of wire. I would do this by using different diameters of wire but using the same length. The reason for the diameter of the wire affecting the resistance is almost the same as for the length. If one increases the diameter of the wire one is increasing the amount of particles which the electrons can collide with therefore increasing resistance.

2 Definition from www.energyquest.ca.gov

Y:\svn\trunk\engine\docs\working\working\29952.doc                Page  of

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