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Resistance of a Wire

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Resistance of a Wire


This coursework seeks to investigate how the resistance of a wire is affected when the length of a wire is increased or decreased. The purpose is to see how the length of a wire affects the dependent variable, resistance.

What is Resistance?

Electricity is something that shares a part in our everyday lives. Electricity is usually converted from one form of energy to another. It starts of as electrical energy and can then be converted into a variety of different energies such as; heat energy, kinetic energy light energy, sound energy, etc. A good example of this conversion of energy is a stereo; it converts electrical energy into sound energy. However not all the energy inputted is given out as a useful energy (in this case sound), some energy is wasted, in this case some energy is wasted as heat.

In the production of such conversions or other electrical circuits, there is a usually a flow of a large collection of negatively charged electrons being carried around a circuit. These large collections of electrons make up the charge, and when the charge moves; an electric current is formed. This charge is also known as the current (I). The more charge flowing the larger the current. The current is measured in amps using an ammeter. An ammeter must always be placed in series in the main part of the circuit.

However this charge needs a pushing force, to push it around the circuit. The charge is pushed around the circuit by a cell. The cell gives out voltage or otherwise known as potential difference (p.d.). The amount of voltage that is given out by the cell is measured in volts, usually by a voltmeter.

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The independent variable of my experiment will be the change in the length of the wire. The dependant variable of the experiment will be the readings of the voltmeter and ammeter which I will use to determine the resistance of the wire. Apart from this, there will also be certain variables that will be kept constant throughout the course of the experiment, in order to carry out a fair test. These variables are as follows:

  • Voltage give out by power pack
  • Material of the wire
  • Thickness of the wire
  • Temperature of the wire

I will keep these above variable constant and same in order to keep the experiment fair throughout. If I was to change any one of these at a given point, then the readings could alter, and the wrong resistance would be recorded.


Before the start of the experiment we had to decide what material of wire we were to use. We were given a choice of wires, ranging from copper, nickel and nichrome. Having done a bit of research, I realised that nichrome would be the best material of wire to select compared to the other two. Thus we chose nichrome and selected it for further work.

Having chosen the wire material, we now had to decide at what voltage setting we were to keep the power pack at, i.e. we had to decide how much voltage would be given out to the electrons. Thus we tested the power pack with a voltage setting of 5V with a 10cm wire sample. This took quicker than expected and the wire melted too quickly. Hence, this meant that the overall experiment would be too quick and short. Thus, we decreased the voltage, in order to increase resistance and lengthen the experiment.

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Apart from the anomaly my points were very accurate because the straight line of best fit proves that the length of the wire is directly proportional to the resistance. Furthermore, the graph also proves that an increase in the length of the wire results in an increase in the resistance.

If I was to repeat the experiment, we could use a different factor to test against resistance, rather than using the length of the wire as the factor. For example, we could test the cross-sectional area of the wire as a factor. If this was the factor we would test against resistance, my prediction would be that an increase in the cross-sectional of the wire would result in lower resistance and vice-versa. In other words, using a thicker would mean less resistance and using a thinner wire would mean a higher resistance. I say this because if there is a thinner wire used, then there would be less space for the flowing electrons to flow through causing more difficulty and this would consequently mean higher resistance. Furthermore, using a thicker wire would create more space for the flowing electrons to flow through; this would mean less difficulty for the flowing electrons and would consequently mean less resistance.

Additionally, I believe that the anomaly was not all bad news. I say this because the anomaly proves that higher temperature does mean higher resisitance.

I believe that we carried out the investigation very well and safely. We used all the right equipment and used it professionally. We took into account all the safety procedures before starting the investigation and practiced them throughout. There were no mishaps to report of, no accidents or anything like that.

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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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