How the resistance of a wire varies with length

The purpose of this coursework is to find out how and why resistance varies with the different lengths of the wire and to study weither resistance obeys Ohm’s Law. I will do so by writing the following coursework ‘How the resistance of a wire varies with length’. I will write this coursewrork in the following order: Background Information, Prediction, Apparatus, Diagram, Method and How I Will Make it a Fair Test, Results, Graph, Conclusion and Evaluation.

Background Information

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The bigger the resistance of the components in a circuit, the smaller the current. The wire connecting the components in the circuit is made of thicker copper wire. This causes negligible resistance to the current.

During the 1820s, a German physicist, Georg Ohm investigated the resistance of different metals. The unit which we now use for resistance is the ohm in honour of him. Ohm’s law is the voltage is proportional to the current.

Prediction

I predict that after I have found the average voltage, current and then found the resistance, the graph stating the resistance comparing to the length of the wire, will be at a 45 degree angle, I believe this, because it would have to obey Ohm’s Law. I will have to however be aware of the following: The type of wire must be the same, the diameter of the wire must be the same, the temperature of the wire must be the same and the length of the wire must be the same, otherwise, it would effect the results.

Apparatus

For this experiment, I will obviously have to use the correct apparatus. The apparatus will be as follows:

1 Ammeter

1 Voltmeter

4/6 Leads

Battery Pack

Sellotape

50cm Constanton SWG 30 wire

Crocodile Clips

Ruler

Diagram

Method and How I Will Make it a Fair Test

Firstly, I will set up the apparatus as the diagram above shows. To make sure that the temperature stays the same, the diameter stays the same, the type stays the same and the length stays the same, I will use the same piece of wire, and leave 2-3 minute gaps between each reading. I will record the voltage and current in at least five places. After I have taken all of the readings, I will repeat the experiment again, take down the results, and find the average voltage/current. After finding the average of each the voltage and the current, I will use it to find the resistance, followed by a graph stating the resistance changing due to the length of the wire. I will then write a conclusion, and then an evaluation.

Results

TEST 1

Length of Wire(cm) Voltage(V) Current(A) Resitance( )

50 2.64 0.72 3.62

40 2.53 0.88 2.84

30 2.43 1.09 2.21

20 2.26 1.41 1.59

10 2.00 2.10 0.94

00 0.00 0.00 0.00

TEST 2

Length of Wire(cm) Voltage(V) Current(A) Resistance( )

50 2.66 0.74 3.64

40 2.55 0.90 2.86

30 2.45 1.11 2.23

20 2.28 1.43 1.61

10 2.02 2.12 0.96

00 0.00 0.00 0.00

AVERAGE

Length of Wire(cm) Voltage(V) Current(A) Resistance( )

50 2.65 0.73 3.63

40 2.54 0.89 2.85

30 2.44 1.10 2.22

20 2.27 1.42 1.60

10 2.01 2.11 0.95

00 0.00 0.00 0.00

How I calculated the resistance:

Eg. When the wire was 50cm long:

Resistance=Voltage Resistance=2.65 Restistance=3.63

Current 0.73

Conclusion

My overall conclusion is that the greater current there is, there is more resistance coming through. There is proof of this in the ‘Average’ results table at 0.73A, the resistance is 3.63 , at 0.89A, the resistance is 2.85 , at 1.10A, the resistance is 2.22 , at 1.42A, the resistance is 1.60 , at 2.11A, the resistance, is less. I believe this is because I probably did not set the circuit up correctly. I believe that the results have followed through correctly otherwise.

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