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Resistance of wire.

Extracts from this document...

Introduction

Physics-Coursework

Resistance of wire.

Planning

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. Resistance is measured in ohms. George Ohm came up with a rule for working out the resistance of a circuit:

R=V / I

V : Volts
I : Current
R : Resistance

Aim:

To investigate how the electrical resistance of a wire changes in relationship to its length.

The resistance of a wire depends on certain factors.

· Length of wire

· Temperature at which wire is kept

· The material of wire

· The potential difference or voltage

· Humidity

· Cross sectional area.

· Voltage across circuit

All these factors will have to be kept constant except the length of the wire whilst doing the experiment to ensure that the investigation is a fair test.

I have decided to investigate how the length of a wire affects its resistance because other factors such as temperature are hard to control or vary. There is not a large enough range of materials to investigate how materials affect the resistance of a wire.

...read more.

Middle

Current = Voltage / Resistance

Length of wire

cm

Equation current =    volts / resistance

Current

A

25

1 / 1.1

0.91

50

1 / 2.2

0.45

75

1 / 3.3

0.30

100

1 / 4.4

0.23

125

1 / 5.5

0.18

150

1 / 6.6

0.15

Comparing Preliminary results with accurate results:

Length of wire cm

My Results

Resistance

Ω

Accurate Resistance

Ω

Difference of accurate and my results Ω

25

1.1

1.1

0

50

2.4

2.2

0.2

75

3.3

3.3

0

100

4.5

4.4

0.1

125

5.3

5.5

-0.2

150

6.7

6.6

0.1

My preliminary results are very accurate compared with the results that I have calculated. There is only 0.2 Ω difference between the two results so I think that have chosen a sufficient variable, voltage, and I will continue my experiment as planned without making any changes.

My graph shows the resistance of my results compared to the accurate results done by calculation. The two lines are very similar and I think that I have chosen a good variable to give a good range of accurate results without being too difficult.

Prediction:

I predict that if the length increases then the resistance will also increase e.g. if the wire length double then the resistance will also double. Electric current is the movement of electrons through a conductor. In this experiment the metal wire Nichrome will be the conductor. So when resistance is high, conductivity is low. Metals such as Nichrome conduct electricity well because the atoms in them do not hold on to their electrons very well. Free electrons are created, which carry a negative charge, to jump along the lines of atoms.

...read more.

Conclusion

To take this experiment even further we could extend the length of wire to get more varied results. I predict that the longer the length off the wire the results will become less accurate because the wire will become difficult to measure and the resistance will also get larger. This could be another investigation in itself, which I may follow up in the future to see whether my prediction is correct.

I have used the equation:

Resistance = resistivity x length

                   Cross sectional area

We can use this equation to check how accurate our results are.

Accurate Resistance

Ω

Resistance

Ω

Difference

Ω

1.1

1.02

0.08

2.2

2.04

0.16

3.3

3.125

0.175

4.4

4.348

0.052

5.5

5.556

0

6.6

6.667

0

As you can see I have compared my results with the accurate results from the equation. I have put both of the results from above onto my final graph.

I think my investigation has gone very well and I also think I have gathered a set of accurate, fair results.

Zuky Batten 10W

...read more.

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