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Resistance Investigation

Extracts from this document...

Introduction

Background Knowledge

Resistance is the opposing force of the conductor to the current. This means that electrons move more easily through some conductors than others when a potential difference is applied. A good conductor has a low resistance and a poor conductor has a high resistance.

The resistance of something depends on its dimensions, and its materials. All conductors have some resistance, however:

image01.jpg

Temperature also affects the resistance of a material, in fact, the resistance of most conductors is found to vary with temperature. In 1826, George Ohm discovered that the current flowing through a metal wire is proportional to the potential difference across it, providing the temperature remains constant.

Ohms law V=IR

Resistance is measured in Ohms (Ω)

In metals, the electrons in the outer shell become detached from their parent atom, so are then able to move better between the positive ions which arrange themselves in a regular lattice.

image02.jpg

The material the conductor is made of affects the resistance. A good conducting material has more ‘free’ electrons than a proper one, and if these electrons can flow easily through the metal, its resistance is lower.

image03.jpg

...read more.

Middle

4.  I switched off power pack and moved crocodile clip down

5.  I repeated it and got an average

6.  Used Ohm’s law V=IR as I have measured the current and voltage

Results

Experiment 1.

L e n g t h

C u r r e n t

50cm

75cm

100cm

125cm

150cm

0.1A

0.56

3.40

1.19

1.37

1.63

0.2A

1.17

2.55

3.39

4.25

5.06

0.3A

1.73

1.76

2.36

2.83

3.40

0.4A

2.31

3.35

4.64

5.61

6.80

0.5A

2.86

4.26

5.70

7.09

8.54

Experiment 2.

L e n g t h

...read more.

Conclusion

image08.jpg

Ohm’s law: The current flowing in a wire is proportional to the voltage across it, providing the temperature is constant.  V=IR

Evaluation

From looking at my graphs, current against voltage,  I could see the current was proportional to the voltage - Ohm’s law. I found out that the steeper the graph, the lower the resistance, and the flatter the graph, the higher the resistance. A substance that gives a straight line graph is called an ohmic conductor.

I found a few anomalous results on my graphs. I think this is because while carrying out the experiment, it was difficult to situate them at the exact points apart from each other. Also, each time I carried out an experiment, it might have been better to let the wire cool down, or at least cut different pieces of wire.

Another experiment I could carry out for resistance against length would be to use a lamp, and note the brightness of the lamp, and see whether the resistance decreases or increases.

image09.jpg

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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