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# To investigate how the resistances of a metal alloy (constantan) is affected by the length of the wire and by different amounts of voltages.

Extracts from this document...

Introduction

## A/S Physics Coursework - Resistance of a Wire

AIM

To investigate how the resistances of a metal alloy (constantan) is affected by the length of the wire and by different amounts of voltages.

## Theory

What is resistance?

Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with other free electrons. This happens across the length of the wire, and allows electricity to be conducted. Resistance occurs when collisions between the free electrons and the fixed particles of the metal and other free electrons occur. This converts some of the energy carried by the electrons into heat energy, and this is resistance.

How is resistance calculated?

The resistance of a length of wire is calculated by measuring the current present in the circuit and the voltage across the wire. These measurements are then applied to this formula:

V = I * R

This can be rearranged to:

R = V/I

Middle

0.6

0.12

5

100

0.7

0.14

5

100

0.8

0.14

6

100

0.9

0.16

6

100

1.0

0.18

6

average resistance

5.1

Length (l)

Voltage (V)

current (A)

resistance Ω

90

0.1

0.02

5

90

0.2

0.04

5

90

0.3

0.07

4

90

0.4

0.10

4

90

0.5

0.12

4

90

0.6

0.14

4

90

0.7

0.16

4

90

0.8

0.18

4

90

0.9

0.2

5

90

1.0

0.24

4

average resistance

4.3

Length (l)

Conclusion

Also as I continued to take down results I realized that even though I was leaving the wire with 30 seconds to cool down in-between different lengths it still remained hot as I continued to write down results. If I were to repeat the experiment I would allocate a greater amount of time to take results and in turn more time to allow the wire to cool between results instead of having to continue the experiment with the warm wire.

Another problem was that arose was the equipment I had to use, it was unreliable and took me some time to find enough working components to complete the circuit. If I were to repeat the experiment I would use more up to date equipment which would lead me to more accurate results.

And finally the last thing I would add to my experiment to improve it would be to collect more results. This would enable me to draw a more accurate graph of my results and then in turn allow me to reach a better conclusion.

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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