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# Investigating the Factors That Affect the Resistance of a Wire.

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Introduction

Investigating the Factors That Affect the Resistance of a Wire

Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire.

There are four main factors that affect the resistance of a wire. These are:

• the length of the wire
• the width of the wire
• the temperature of the wire
• the material of the wire

Each of these is able to change the resistance.

• As the length of the wire increases, the resistance increases. If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this
the length increase should be proportional to the resistance increase.
• As the temperature of the resistance wire increases, the resistance of the wire increases. This is because if the wire is heated up the atoms in the wire will start to vibrate more because of their increase in energy. This causes more collisions between the electrons. This increase in collisions means that there will be an increase in resistance.
• Material of the wire also affects the resistance. The type of material will affect the amount of free electrons which are able to flow through the wire. The conductivity of the material dictates the amount of resistance that will be created as the electrons pass. Metals are good conductors because the particles are close together so the vibrations of the electrons are passed long quickly. Metals also have many free moving electrons which travel through the metal carrying the electrons with them. Copper wire will create a low resistance because copper is a good conductor.
• As the width of the wire increases, the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the electrons, there are less collisions are so less resistance is produced.

I have decided to investigate how the length of the wire alters the resistance as I feel that this experiment will be the most feasible and produce the most accurate results.

This is the circuit that I am going to use to investigate how the resistance of the wire changes as I vary the length of the wire.

The apparatus that I shall need in order to carry out this practical is:

• a power pack
• an ammeter
• resistance wire
• a voltmeter
• crocodile clips

Middle

30

1.20

3.18

2.65

40

1.03

3.33

3.23

50

0.92

3.45

3.75

60

0.85

3.52

4.14

70

0.78

3.58

4.59

80

0.76

3.61

4.75

90

0.74

3.62

4.89

100

0.74

3.62

4.89

 Length (cm) Current (A) Voltage (V) Resistance (Ω) 10 2.32 2.40 1.03 20 1.56 2.89 1.85 30 1.20 3.19 2.66 40 1.03 3.33 3.23 50 0.92 3.44 3.74 60 0.85 3.53 4.15 70 0.79 3.58 4.53 80 0.76 3.60 4.74 90 0.74 3.63 4.91 100 0.75 3.62 4.83
 Length (cm) Current (A)

Conclusion

EVALUATION:-

I felt that my experiment was not carried out accurately as although the results followed my prediction, they were not the expected results. I think that this was due to the wire overheating whilst taking measurements. However, I feel that my results were as accurate as possible because they formed a smooth curve on the graph and the repeat readings were very similar. I did not receive any anomalous results as all my results fit with my line of best fit.

In order to improve my experiment, I feel that I should measure the length at every 5cm to receive more points on the graph to be sure of its shape. Also, a wider range of readings could be taken, perhaps up to 150cm; to see if a t any point the graph would start to level off. In addition, I would take steps to reduce overheating of equipment as this tends to distort results.

From my investigation, I can conclude that as the length of the wire increases, the resistance increases. This is supported by the smooth curve on my graph and the similarity in my repeat readings.

Zilia D’Mello        Page         Physics Coursework

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