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Factors affecting the resistance of a wire.

Extracts from this document...

Introduction

Hannah Marchant

Coursework

Factors affecting the resistance of a wire

Introduction:

Resistance is a force, which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. E.g., The filament across an electric bulb is quite thin as it needs to resist the flow of particles for the bulb to glow.

Resistance is measured in ohms. George Ohm discovered that the electromotive force of a circuit is directly proportional to the current flowing through the circuit. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit :

V/I = R

V - Volts

I - Current

R - Resistance.

Plan: Three external factors influence the resistance in a conductor. Thickness (cross sectional area of the wire), length, and temperature all have some effect on the amount of resistance created in a conductor. The fourth factor is the conductivity of the material we are using. Some metals are just more electrically conductive than others are. This however, is considered an internal factor rather than an external one.

For the

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Middle

 we will observe the reading on the voltmeter change as we change the current to 0.25 A. We also observe a general increase in the voltage, as the length of wire we use gets longer. The rheostat will also be set at different positions for the different lengths of wire that we use.

Evidence: to make sure our overall values are as accurate as possible we will repeat our readings and then take the mean resistance. We will also be able to spot and discard any anomalies from our results.  

Results:

Set of results 1

Amps

(V) Volts

(   ) Amps

cm

I

V

resistance

6

0.25

0.11

0.44

12

0.25

0.21

0.84

18

0.25

0.33

1.32

24

0.25

0.43

1.72

30

0.25

0.54

2.16

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Conclusion

I do not think that doing any more results in our experiment would have made it any more accurate.

        During my experiment, I have noticed several modifications I could make to improve on the Investigation if I was to repeat it. I could use pointers instead of crocodile clips; I would do this because pointers would be more accurate. The pointers would be more accurate because the tips have a much smaller area than the crocodile clips giving a more accurate measurement of the length of wire. Perhaps where we to have a bar that didn't bend in place of the wire, it could have been more accurate.

As well as making these modifications, I would also improve my Investigation by testing the same wire but with different widths of that wire. I would do this to expand on my Investigation. I could also try to work out the resistivity of the wire, we could do this by using the formula (                  ) and then work out the percentage of error in our results.

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