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The Electrical Resistance of a Wire.

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Introduction

The Electrical Resistance of a Wire

Aim

I am going to be studying the resistance of wire. The purpose of this investigation is to see how the length of a wire affects the dependent variable, resistance.

My Prediction and Hypothesis

I predict that if the length increases then the resistance will also increase in proportion to the length. I think this because the longer the wire the more atoms and so the more likely the electrons are going to collide with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled the numbers of atoms will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. I predict this because resistance of a wire is the slowing down of the current electrons in the wire by atoms of the wire. The current is the flow of free electrons along the wire.

I am going to plan an investigation to find out if my prediction is correct. In this plan I am going to set up a circuit to measure the current through a wire and the potential difference (voltage) across it. I will then use the formula resistance =,                       to calculate the resistance of the wire.image00.png

Plan

In this investigation a simple circuit will be set up to read the voltage and current when the length of the wire changes. My plan is to find the best results by observing resistance of different sized wires.

...read more.

Middle

 Length

In  cm

1

2

3

Average

1

10.0

10.0

10.0

10.0

2

19.5

19.7

19.6

19.6

3

30.0

30.0

30.0

30.0

4

39.9

39.9

40.0

39.9

5

50.1

50.0

50.1

50.1

6

60.2

59.9

60.0

60.0

7

70.1

70.2

70.1

70.1

8

80.0

80.0

80.0

80.0

9

90.1

90.2

89.9

90.1

10

99.4

99.2

99.3

99.3

Voltage and current

These are the results of the average wires from above. These also have been tested three times and average was made for voltage and current.

...read more.

Conclusion

There are no anomalies in my graph so these results were very good and reliable. Although not all of the points are exactly on the line. This could be because we measured the length of the wire we were trying to use wrong so we got a different reading to what we wanted. Also the temperature could have gone up a bit if we didn't disconnect the circuit after each reading, and as we know the resistance will change if the temperature changes. Also we could have used a different cross sectional area but still changing the length. Another reason why the points were a little off the line sometimes is that we might not have measured the length of wire right as the crocodile clip does not always test the full length of the wire. To improve the results I could use screw clips which would test the full length of the wire and measure the thickness of the wire at various points to ensure it’s the same.

To gather more relevant evidence we could have done the experiment with a different metal just to see if the resistance still went up when the length was increased. The resistance would change in this new wire depending on how many atoms were in the wire. Also we could have changed the width of the wire and I think that as the width of the wire got larger the resistance would decrease, as there would do more room for the electrons to move.

...read more.

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