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Determine how the effect of electrical resistance changes with varied length of a metal wire.

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Electrical Resistance Coursework


This coursework is based on the topic of electrical resistance.  The aim of this coursework is to determine how the effect of electrical resistance changes with varied length of a metal wire, which is the factor I will be investigating.  In order to do this, I will measure the resistance of the wire at equal length intervals, using a voltmeter in parallel and ammeter in series, and then record the change in resistance in relation to the length of the wire.  In the end I am going to find out as to how resistance of a metal wire varies in relation to the length of the wire used.  

Theoretical Background

        Firstly, resistance shall be dealt with.  Electrical resistance is the opposition to the flow of electric charge (current).  With a given energy source, such as a battery, the size of the current that flows is determined by the resistance of the circuit.  All conductors resist the flow of electric charge to a certain extent, but some conductors are better resistors than others.  The bigger the resistance of a conductor, the harder it is for electric charge to flow through it.

        With a conductor of high resistance, the amount of charge flowing through it is reduced, and energy is released, resulting in the conductor becoming hot, due to friction.

        Resistance can be defines as the ratio of the voltage across an object to the current flowing through it.  The formula to work out the resistance is:

...read more.


increase in resistance, due to frequent collisions.

To do this I would use the same length and width of many different wire materials, using the same amount of voltage each time.

Finally, the length of the wire is a factor. The longer the wire, the longer it will take electrons to get to the end of the wire. This is because there will be more collisions between electrons and atoms. So, in theory, the length of the wire should be directly proportional to the resistance.

This would be very easy to do, and give accurate results. Because of the length being proportional to the resistance, I could link the length of a wire with the resistance of the wire, which would make my graph more interesting.

Due to the effectiveness of this method, I have decided to use the length of the wire as the factor that I am going to use.


I predict that, the longer the wire is, the more resistance there will be due to more collisions between the electrons and atoms. The length of the wire should be approximately proportionally the same as the resistance. In theory, if the wire is doubled, then so will the resistance. If the length is twice as much, then there will be twice as much collisions, which would increase the resistance.



· Crocodile clips

· Ammeter

· Voltmeter

· Power supply

· Meter ruler

· Connecting wires

· sticky tape

· Thin Constantine wire


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As you can see in the diagram, the wire on the top is twice as big as the one below it, so it has twice the electrons too.


This experiment has gone satisfactory, but there have been certain things in the experiment that I have not been pleased with.

Some of my results have turned out anomalous. This mainly being:

60cm Anomalous

























I have probably ended up with this anomalous result because of an error in recording my results.

However, as you can see from my average resistance graph, the results are roughly on the same line, so this anomalous result did not do much harm when the results are averaged.

I have noticed, now that I have finished my coursework, that there are a number of things I could have done to get more accurate results.

Firstly, I would do the experiment using the width and the material used as a factor too, just to make sure that my averages are as correct as possible.

The next thing I would have done is to use pointers instead of the crocodile clips which I used. This is because pointers are a lot more accurate, because they have a smaller surface area on their tips than crocodile clips. This in effect would give much more accurate measurements.

...read more.

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