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# To investigate how the resistance of a wire varies with its length.

Extracts from this document...

Introduction

Holly Atkins                  Page:

Practical:

To investigate how the resistance of a wire varies with its length

Equipment Needed:

• power pack
• 5 wires
• Voltmeter
• Length of wire
• Ruler
• Ammeter
• Crocodile clip

Circuit Diagram:

Prediction:

The equation V=IxR is how you find the resistance rate. I’m now going to re-arrange it to R= V    for this to work the temperature has to stay

I

Constant or it will not work. So I predict that if I increased the length of the wire the resistance will be increased. So I think that if you double the length of the wire the resistance will be doubled.

Method:

• Collect the equipment and set up the circuit by measuring the wire
• Turn on the power pack
• Slowly increase the power
• Connect the crocodile clip onto the copper wire to make the circuit complete.
• Using a ammeter to measure the amount of current in the circuit
• Using a voltmeter to measure the amount of voltage across the circuit
• Record results

Middle

0.5

1.2

1.0

60

0.5

0.7

0.6

1.4

1.2

70

0.5

0.8

0.7

1.6

1.4

80

0.5

0.9

0.8

1.8

1.6

90

0.5

1.1

1.0

2.2

2.0

100

0.5

1.2

1.1

2.4

2.2

 Length(CM) Current (A) Voltage (V) Corrected Resistance(  ) Corrected 0 1.0 0.1 0.0 0.1 0.0 10 1.0 0.3 0.2 0.3 0.2 20 1.0 0.6 0.5 0.6 0.5 30 1.0 0.8 0.7 0.8 0.7 40 1.0 0.9 0.8 0.9 0.8 50 1.0 1.3 1.2 1.3 1.2 60 1.0 1.4 1.3 1.4 1.3 70 1.0 1.6 1.5 1.6 1.5 80 1.0 1.8 1.7 1.8 1.7 90 1.0 2.1 2.0 2.1 2.0 100 1.0 2.4 2.3 2.4 2.3
 Length(CM) Current(A)

Conclusion

This all happens because the resistance has doubled like I said in my prediction. I checked this by looking on my graph

E.g. 20CM= 0.44

40CM=0.88

80CM=1.76

See each time it has doubled.

Evaluation:

We found out that there was an error in our voltmeter which meant our first point was on 0.1. This made our results incorrect which meant we had to re calculate the numbers.

We read all our results to one decimal point instead of two.

I have an Anomalous point at 20cm. I can see from my results there was a error at 15amps. If I ignore this result and take an average of 0.5+1.0amps I get a point that lies on my line. I have shown this on my graph in red. This error accrued by reading the metre wrong.

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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