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# Resistance of a Wire

Extracts from this document...

Introduction

GCSE Science Coursework

Resistance of a Wire

Introduction

Resistance in a wire occurs when electrons collide with metal ions as they travelling through. This is called the collision theory. The electrons exist in clouds around the ions. If a potential difference is applied, the electrons in the cloud are able to move.

As the electrons collide with the metal ions, a resistance is created in the flow of electrons.

A very high resistance, causes a very low current and vice versa.

The positive metal ions have gained a charge because they have donated electrons into the ‘sea’ of electrons. As they now have more protons than electrons, they are positively charged.

This sea of electrons is responsible for holding the metal atoms together regularly.

Factors affecting the resistance in a wire

1. Length of the wire

This is a factor because as the length of the wire increases, the electrons have a larger distance to travel. This results in more of a chance that electrons will collide into the metal ions. Resistance is proportional to length, so if the length of the wire is doubled, the chance of collision is also effectively doubled. This is because the amount of metal ions in the wire has increased.

1. Cross-sectional area

The greater the cross-sectional area of the wire, the more electrons there are in the wire to carry the charge.

Middle

ST TEST

2ND TEST

3RD TEST

AVERAGE RESISTANCE

(Ω)

LENGTH

V (V)

I (A)

R (Ω)

V (V)

I

(A)

R (Ω)

Conclusion

Before I came to the conclusion that nichrome was the most suitable, I had tested two other wires. These were copper and aluminium. The readings on the ammeter kept going off the scale at even very low temperatures. I found out the reason was because copper and aluminium are excellent conductors of electricity.

If doing this experiment again, a higher accuracy of results could be achieved. This could be possible if using digital voltmeters and ammeters. Or if possible, an Ohmmeter would be an excellent aid. Analogue meters can be a problem if their primary reading is a little. This could be due to misuse or accidentally dropping them on the floor.

Although I didn’t receive any anomalous results, to avoid this from happening in the future, I will have to check that all apparatus is set up properly and that nothing is touching the wire under test.

To extend this experiment, I could use the same type of wire, but see how it performs when I use different thicknesses. This thickness of the wire would be the variable, because the cross-sectional area of a wire is a factor that changes the resistance.

Another variable could be the temperature at which I do the experiment. I could possibly do the experiment outdoors to lower the temperature.

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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