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The aim of this investigation is how the resistance of a nichrome wire changes as the length of the wire changes.

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Sohail Ali 10.403/04/01

Science Coursework

An Investigation on Resistance of a Wire


The aim of this investigation is how the resistance of a nichrome wire changes as the length of the wire changes.

Background Knowledge

Ohms law states a relationship between voltage (V), current (I) and resistance (R). If the voltage is increased then more current will flow, but if the resistance is increased this will decrease the flow of the current.

        This is because the resistance is conflicting with the flow: it makes it difficult for the electrons to pass around the circuit therefore slowing the flow down.

        The voltage is in fact a driving force, pushing the current around the circuit. The voltage supplies the push for the current to pass around the circuit and pass the resistance in the circuit; the amount of resistance and voltage decides how the amount of current passing through the circuit. If two of the three principles are available, then the following formula may be used to calculate the third.

V = IR

Resistance is proportional to the length of wire, this according to various textbooks. Therefore a prediction should consist of; the greater the length of wire the higher the resistance.

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4) Keep everything constant except the length of wire.

5) Switch on the circuit for only a short time (Otherwise the                     wire would have got hot and resistance would increase, therefore making the test unfair)

6)  Read the current using the ammeter.

7) Read the voltage using the voltmeter.

8) Record results in a table.

9) Worked out the resistance using Ohms law:

Resistance (Ω) = voltage across wire (V), current through the wire (I).

10)        Repeat this method, now simply

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Ω). This also backed up my prediction.


I think my results were as accurate as they could be, as the readings were rounded up to 2 dp. So the results weren’t 100% accurate.

I think that the experiment was generally a fair test but in some ways it wasn’t for example the length of the wire was not always exact maybe a couple of mm difference. Temperature is one of the key factors of resistance; for example in our experiment the temperature of the wire was high therefore the resistance become greater. It affects the resistance by making it higher as the electrons move faster at higher temperatures. I don’t think this experiment could be made any fairer as we did everything that we could to make this a fair test because the only way to make the experiment fairer was to be more accurate with the measuring of the wire. There are many different ways of extending our work to get more answers on the different affects on resistance. One way is by seeing how the thickness of a wire would affect the resistance. Or by experimenting with different materials and how they affect resistance.

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