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Investigating wires and resistance.

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Introduction

Physics coursework – investigating wires and resistance

I am going to perform an experiment to investigate the resistance of a wire.

The factors that I could change are:

  • Length of a wire
  • Voltage
  • Thickness of the wire
  • Temperature
  • Material the wire is made of

The factors I could observe are:

  • The voltage
  • The resistance
  • The temperature
  • The amps

I will keep everything constant but I will vary the length and observe the resistance.

Resistance

(Ohms)          

                Length (cm)

My prediction is that the resistance will increase in direct proportion to the length of the wire.This means that when you double the length the resistance will also double. I also predict that the line of best fit will go through the origin.

When a charge flows through a wire they get slowed down when they hit positive ions this generating a lot of heat this slowing down of electrons is called resistance. A charge is a flow of negative ions. As my wire gets longer the resistance will increase if I

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Middle

60

0.05

0.9

18

70

0.05

0.9

18

80

0.05

0.9

18

Below are some of the problems I encountered in my dummy run:

  • I used quite a short piece of wire this caused the wire to become very hot increasing the resistance. This stopped it being a fair test because the temperature did not stay constant
  • The results reached there maximum resistance this will hopefully also be solved by a longer wire
  • To solve this I am increasing the length of my wire from 80centimetres to 1metre I will take results every 10centimetres.

The only change I will make to my method will be to take two more readings at 90cm and 100cm. I will make readings at 0cm, 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm.

To make this experiment a fair test I will only change the length of the wire I will not change anything else. I will keep the wire the same thickness because if the wire is thinner there is less room for the negative ions to flow. The wire will be made of the same material throughout the experiment. I will keep the voltage the same and I will keep the wire at room temperature throughout this experiment because if I change the increase the temperature then the positive ions will move about more making it harder for the negative ions to pass through. To make sure my results are also fair I will repeat the experiment and take all my readings again.

Attempt 1:

Length of wire (cm)

Amps (a)

Volts (v)

Resistance

0

0

0

0

10

0.49

0.58

1.18

20

0.27

0.63

2.33

30

0.19

0.66

3.47

40

0.15

0.69

4.6

50

0.12

0.70

5.83

60

0.10

0.71

7.1

70

0.09

0.71

7.8

80

0.08

0.72

9

90

0.07

0.72

10.29

100

0.06

0.73

12.16

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Conclusion

To further improve the accuracy of my results I could take readings every five centimetres and I could take readings from 0cm to 200cm. This would mean I have a bigger and more accurate range of results. I could also leave the wire for a few minutes after each reading to make sure it cools down to room temperature. I could also make three or four readings at each length.

My graph is reliable because all the points fit onto my line of best fit and my graph is directly proportional and it goes through the origin. I do not have any anomalous results that don’t fit onto my line of best fit.

To further investigate resistance I could repeat the experiment but changing the heat and keeping the length of the wire constant or I could change the amount of volts I pass through the wire.  

Ben Wilkinson 11PA

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