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Resistance of a Wire Investigation

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James Rooney

Resistance of a Wire Investigation


Electricity is the flow of free electrons in a metal.   These electrons usually move randomly through an atom but when a charge is added the metal gains positive and negative ends.   The electrons are attracted to the positive ends.   Other atoms in the metal will slow down the electron and it will ‘bounce’ around in the metal until it reaches the positive end of the wire.   The longer

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electron                                        electron

The voltage of a circuit is how much power is being run through it.   The higher the voltage gets, the more you are having to push to make the current move.   The current is the flow of the electricity in the actual circuit, due to the number of electrons mowing around it.

Making the piece of wire longer should make the resistance higher because the electrons have to travel a greater distance and pass a greater number of atoms without colliding to reach the positive end.

Changing the cross-sectional area of the wire should also change the resistance.   Making it larger lowers the resistance because the electrons would have more space to move in and so it would be much easier for them to move to the end of the wire.

Changing the material means that there are different numbers of atoms and electrons so the resistance will change.   If there are more atoms and fewer electrons then the resistance will increase as fewer electrons can reach the end.   If there are more electrons and fewer atoms then the resistance will lower as more electrons can reach the end.

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My results seem to be accurate as they follow a trend, which creates a straight line on the graph.   This proves that there is a direct correlation between the length and the resistance of a wire.  

The experiment went well and there were no problems with either collecting or analysing the data.   I could improve the way I collected the data because I do not think that all of the measurements were made at exactly the right lengths.   This may help to explain why the line on the graph does not go through the origin but crosses the X-axis at around 4 cm.   I also saw that the temperature of the wire increased when length began to get towards 1 metre.   This changed the resistance of the wire and so it was not a fair test in this respect.   Turning the electricity on for a shorter time, giving the wire no chance to heat up, could alter this.

At the end of the graph, there is a slight curve upwards.   This is where the wire had heated up and caused the resistance of the wire to increase.

To extend the inquiry into the resistance of the wire I could have tested to prove whether the cross-sectional area or temperature of the wire affected it’s resistance.

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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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