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Effect of Wire Length of the Resistance of the Wire

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How wire length affects resistance?

What is current?

        Current is the rate of electrical energy that flows past a given point in an electrical circuit in a given time this is measured in amperes. In most circuits it can be assumed that the resistance to current flow is a constant this means that the current in the circuit is related to voltage and thus resistance by Ohms law.

                I        =        V/R

Electrical Current        =        Voltage/Resistance

What is voltage?

In order for a current to flow, something has to make it flow. That something is measured by voltage. The more charge that flows through a wire in each second, the bigger the current.

What is resistance and how can it affect electricity?

        Resistance is when a wire resists the movements of electrons within it. This means that the wire has a resistance to the electrical current. The more resistance the wire gives, the more voltage is required to push a current through the wire.

To calculate the resistance in a wire use this method:

        R        =        V/I

Resistance        =        Potential difference across the wire/current through the wire

My theory is that the longer the wire length is the more resistance there will

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         The length of the wire and the voltage (Current)

M        The voltage, amps and the wire length.


        My prediction is that as you increase the length of the wire the resistance will increase, as the flow of electrons will be resisted more as there are more particles within the wire to resist the flow, therefore more voltage will be required to push the current through.

(Rough Estimate)

Ω             V         A        V        A        V        A        V        A

10         0.71           1        1.4        2        2.8        3        4.2        4        5.6

20         1.42           1        0.7        2        1.4        3        2.1        4        2.8          

40        3.5       1        0.4        2        0.8        3        1.2        4        1.6

60              5       1        0.2        2        0.4        3        0.6        4        0.8

80         6.66           1        0.15        2        0.3        3        0.45        4        0.6

100          10       1        0.1        2        0.2        3        0.3        4        0.4

        My theory behind the prediction is that as you increase the length of the wire, you also increase the resistance, as described above and in my theory, as you double the voltage, the reading on the ammeter should also be doubled or near enough for example 1 volt = 0.9 on the ammeter 2 volts = 1.8 etc.

        Also as the length of the wire is increased for example if it was doubled the resistance would be twice as much e.g. 10cm of wire has resistance of 0.71 and 20cm of wire has resistance of 1.42.


        That all the electrical equipment I will be using will have been tested for safety and that my plan for finding resistance is approved by the teacher.

Preliminary Experiment.

                V        A        V    A              Ω

10cm.        1     1.27        4     4.8      0.8085         

Ω        0.787               0.83        

100cm.        1        0.12        4     0.46    8.51

Ω        8.33            8.69

Conclusion my Preliminary Experiment.

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What is resistance and how can it affect electricity? For wire length theory)

        The final results I find to this experiment are to my liking as the results follow a similar pattern to that of my prediction i.e. 1 volt = 0.9 on the ammeter 2 volts = 1.8 etc. this to me means a success as the experiment has done what I thought it would do.


        I found that the method that I used was suitable to the experiment and the experiment proceeded without a fault and the evidence which I obtained of discovering how wire length effects resistance was very conclusive for as the results show, resistance does increase as wire length is increased. The results obtained also show that the experiment was reasonably accurate as the results obtained varied only marginally (at a difference of 0.4 either side at the most), which shows that the method was also good enough for the purposes of this experiment.

If I were to do this experiment again though, I would choose a much wider variety of wire lengths and wire types, and repeat each voltage for each wire length at least 3 times to get an accurate average for each wire length, for I find that these few results do not offer enough variety to provide sufficient evidence to support my theory (title), following that I would also like use the same equipment throughout the experiment to avoid any possible differences within the equipment.

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