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# To find out how the length of a wire affects its resistance by carrying out an investigations

Extracts from this document...

Introduction

Coursework

## Resistance in a wire

Aim:

To find out how the length of a wire affects its resistance by carrying out an investigations.

Background Information:

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. Measurements of electrical resistance is taken in ohms, the formula for working out resistance is:

Resistance = potential difference  / current

To measure current you place an ammeter in series with the components.

Potential difference is measures by using a voltmeter in parallel with the components. Resistance is anything in a circuit which slows down the current.

Preliminary Experiment:

Middle

40

1.87

0.82

50

1.98

0.5

60

2.04

0.41

70

2.1

0.38

80

2.15

0.34

90

2.18

0.3

100

2.22

0.27

Prediction:

I predict that if the length increases then the resistance will also increase in proportion to the length. I think this because the longer the wire the more atoms and so the more likely the electrons are going to
collide with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled the number of atoms will also double resulting in twice the number of
collisions slowing the electrons down and increasing the resistance
. This is backed up by the results of my preliminary experiment.

Method

In this experiment I will select a wire

Conclusion

Results:

LENGTH      20 cm           400 cm        60 cm            80 cm          100 cm
VOLTS (v)|  1.6 1.5 1.6 |1.7 1.7 1.7  | 1.8 1.8 1.8  | 1.9 1.8 1.8  | 1.9 1.9 1.9

AMPS (I) 20cm           40cm               60cm              80cm            100cm

|0.61 0.60 0.61|0.35 0.35 0.34|0.23 0.24 0.24|0.18 0.19 0.18|0.14 0.15 0.15

RESISTANCE (Ohms) 20cm     40cm        60cm          80cm            100cm

|2.6 2.5 2.6|4.8 4.8 4.8|7.6 7.6 7.6|9.9 9.8 9.8|12.8 12.8 12.8
AVERAGE RESISTANCE
2.6               4.8         7.6                10.0            12.8

From these results I have drawn a graph of the length of the wire and the resistance of the wire.

From the graph on the excel page I can see that the resistance of the wire is proportional to the length of the wire. I know this because the Line of Best Fit is a straight line showing that if the length of the wire is increased then the resistance of the wire will also increase.

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