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Factors affecting the resistance of a wire

Extracts from this document...

Introduction

RESISTANCE OF A WIRE INVESTIGATION

Skill Area P; Planning Experimental Procedure

Hypothesis

Four factors affecting the resistance of a wire are:

·  The temperature of the wire.  If the wire is hotter than usual then electrons are given more energy and collision is more frequent.  Therefore the resistance is greater.

·  The length of the wire.  The length of the wire is directly proportional to the resistance and so if the length of the wire is longer, then the resistance of the wire is greater.

·  The width of the wire.  Thick wires have more free electrons per unit cross-sectional area than thin wires.  Therefore thicker wires will have a larger resistance than thinner wires

·  The metal that the wire is made out of.  Some metals conduct heat easier and quicker than others.  All metals are good conductors because there are lots of free electrons to move between the atoms of the metal.

Prediction

If the length of the wire is doubled, then the resistance will double.  This means that the resistance is proportional to the length of the wire.

As the length of the wire is increased, there are more atoms present for electrons to collide with and therefore resistance is greater.  More and more atoms can also collide and collisions become more imminent.  There are more and more free electrons and when the electrons collide with atoms, energy is transferred to the atoms that start to vibrate and the material becomes hotter.

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Middle

90.0

0.40

3.64

9.10

90.0

0.50

4.53

9.06

90.0

0.60

5.46

9.10

Average Resistance:

9.04

Length of a wire (centimetres)

Current I (Amperes)

Voltage V (volts)

Resistance R=V/I (ohms)

80.0

0.20

1.59

7.95

80.0

0.30

2.43

8.10

80.0

0.40

3.25

8.13

80.0

0.50

4.05

8.10

80.0

0.60

4.88

8.13

Average Resistance:

8.08

Length of a wire (centimetres)

Current I (Amperes)

Voltage V (volts)

Resistance R=V/I (ohms)

70.0

0.20

1.42

7.10

70.0

0.30

2.15

7.17

70.0

0.40

2.87

7.18

70.0

0.50

3.57

7.14

70.0

0.60

4.30

7.17

Average Resistance:

7.15

Length of a wire (centimetres)

Current I (Amperes)

Voltage V (volts)

Resistance R=V/I (ohms)

60.0

0.20

1.20

6.00

60.0

0.30

1.81

6.03

60.0

0.40

2.44

6.10

60.0

0.50

3.05

6.10

60.0

0.60

3.65

6.08

Average Resistance:

6.06

Length of a wire (centimetres)

Current I (Amperes)

Voltage V (volts)

Resistance R=V/I (ohms)

50.0

0.20

0.99

4.95

50.0

0.30

1.50

5.00

50.0

0.40

2.04

5.10

50.0

0.50

2.53

5.06

50.0

0.60

3.07

5.12

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Conclusion

Anomalous Readings

There are no anomalous readings in my results.  All my results are touching or very close to the line of best fit.  This just shows how successful my experiment actually was.  However if there were anomalous readings then I would have identified them on my graph and tables as anomalous.

Improving the Accuracy of the Readings

My readings are very accurate, however if I wanted to make them even more accurate I could use a digital ammeter rather than an analogue ammeter that I used in my experiment.  This way I could simply read the current and the readings would probably be to 2 decimal places.  Therefore my results would be much more accurate.

Improving the Reliability of the Evidence

To improve the reliability of my readings I could have repeated the experiment more times.  Also, I could have even used a much more higher scale with the length of wire such as 10cm to 300cm.  We could also use a data logger to measure readings.  Data loggers are much more accurate as they measure digitally through a computer.  We could also use improved contacts on wire; so we don’t have any rusty wires etc.  We could also use intervals of 5 centimetres to get twice as many points on the graph.

Kai Baker

10 Alpha

Physics Coursework

Mr O’Malley

...read more.

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