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Investigating the Resistance of a wire.

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Investigating the Resistance of a wire.


The aim of my investigation is to find out how the length of a wire affects the resistance of that wire.

Resistance is the force that opposes the flow of an electrical current around a circuit so that energy is required to push the charged particles around the circuit. Resistance is measured in Ohms.

These collisions cause the voltage push to be less affective; this is what resistance means. Resistance is a measure of how hard it is to move the free electrons through the wire.

If the length of a wire is increased then the resistance will also increase as the free electrons will have a further to travel and so more collisions will occur with the static electrons. Because of this, the length increase should be directly proportional to the resistance increase.

I have chosen to investigate how resistance changes with length this is because I have decided to prove that resistance is directly proportional to length.


        I predict that the longer the piece of wire is then the higher the resistance of that wire will be. This is because as the free electrons from the power supply are colliding with the electrons of the atoms, which make up the metal and they would also be colliding with any impurities in the metal, this will result in the resistance being doubled.


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              Length of Wire                



  • 6 wires
  • 1 Amp meter
  • 1 Volt meter
  • 1 Power Pack
  • 1 Variable Resistor
  • 1 Metre Ruler
  • 1 Length of wire
  • 2 Crocodile Clips
  • 1 Roll of Tape



        When a voltage is applied to a complete circuit a current will flow. The larger the voltage (or potential difference) the larger the current. This can be expressed by an equation.

                V         =        I        x        R

        Voltage              Current             Resistance

        (Volts)              (Amps)               (Ohms)

          [V]                        [A]                [Ω]

This can also be put into a magic triangle:



                                        I   Rimage16.png


        Within any circuit, components tend to prevent the current from flowing i.e. they resist the current from flowing. The larger the resistance the smaller the current that flows. Alternatively we can say that the resistance is increased then the voltage will need to be increased, to maintain the same current.




The current through a resistor (at constant temperature) is proportional to voltage.image19.png


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        Looking at the graphs I saw a definite pattern, this is that they all have positive correlation, this means they all follow the same inclination. The graphs are an easier way to prove the same as my results table does, it clearly shows that the longer the piece of wire the higher the resistance it causes.


        I think that the experiment went very well as I got all the results I needed to prove my prediction, which I am very pleased about.

        The readings are not perfectly accurate as I was only using a simple voltmeter and ammeter. To make the results more accurate I could use specialised equipment, such as the ones used in industry.

        However, I made certain that my ‘fair testing’ standards were kept to the highest possible standards.

        On my graph there are one or two anomalous results, I can explain these by the fact that I rounded the resistance figures to one decimal place. These could be more accurate if I had not done this, but then it would be harder to assemble a graph using such long numbers. Another way to produce a graph with minimal error is where my results would be rounded to two or three decimal places.

        If I were to do the experiment again I would do a further investigation to find out how the width of a wire affected the resistance of a wire. Also I would work out the restivity of the wire – I could do this by working out the gradient of my graph.

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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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