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To discover how length and cross sectional area of a wire affects the resistance of a wire.

Extracts from this document...

Introduction

Aim:    

     To discover how length and cross sectional area of a wire affects the resistance of a wire.

Prediction:

      In my opinion, I predict that the resistance of a wire will increase with length. I feel this because the electrons have further to travel therefore it has a higher chance of being terminated/stopped by the atoms. I predict the resistance will decrease when the cross-sectional area is increased. I think this because the electrons will have more space to flow past the atoms.

Diagram:

Fair Test:

     To perform a fair test I will manipulate/test one variable at a time e.g. length.

I will keep the following the same:

  • The power pack
  • The voltmeter
  • The other wires
  • The material the wire is made from
  • The temperature
  • I will keep the cross-sectional area the same when monitoring the length and vice versa  

Method:

  • I will set up the apparatus as shown in the diagram above.
  • When a current is flowed through the wire I will record the readings on the ammeter and the voltmeter in to a table.
  • I will then use my results in the formula R=V/I to calculate the resistance of the wire.
  • I will then increase the variable I am analysing and record the data I have mentioned.
  • I will repeat this ten times for length and six times for cross-sectional area.
  • I will try and keep the results reliable by following my fair test above and re-testing my results.
  • By re-testing my result my mistakes should be easy to see (my anomalies).
...read more.

Middle

  1. 16

0.5

3.59

3.72

7.18

7.44

  1. 20

0.5

4.08

4.48

8.16

8.96

  1. 24

0.5

5.10

5.20

10.2

10.4

  1. 28

0.5

5.90

5.93

11.8

11.86

  1. 32

0.5

5.36

6.79

12.72

13.58

  1. 36

0.5

7064

7.53

15.28

15.00

  1. 40

0.5

8.33

3.37

16.66

7.46

Cross-sectional Area:

Constant length is 20 cm:

Cross-sectional area (mm )

Current (amps) (I)

Voltage (volts) (V)

...read more.

Conclusion

Evaluation:

      The first thing I would have to say is that I definitely don’t think I measured the width of the wire because there are many errors (anomalies) on my graph and in my table. Next time I should take longer to measure them and not rush it as I did. I should also do all of my tests and re-tests at the same time to make sure everything is the same. But there is the problem of the allowance of time to do the tests in.

...read more.

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