Investigation into how the resistance of a wire depends on its length.

Authors Avatar

Investigation into how the resistance of a wire depends on its length.

Variables.

        My independent variable will be the length of wire.

        My dependant variable will be the resistance of the wire, found by measuring the voltage (volts – V) and the current (amps – I) and using the following formula: -

V = R

    I

        My controlled variable will be the area of the wire, which I will keep the same as far as is realistically possible.

Prediction

Resistance occurs because as electrons pass along a wire they collide with atoms of the metal and so lose energy. In a longer wire there will be more collisions and so the electrons will lose even more energy.

I predict that the longer the wire is the more resistance there will be.  I believe this will be the case as over a longer distance resistance will have more of a chance to build up, whereas over a short distance the resistance will not have such a chance, and there will be less resistance as a result.  I must keep the area of the wire the same as far as possible as this is not what we are measuring and any change in width may have an effect on the resistance of the wire.

So,

        The longer the wire, the more times the free electrons will collide with other free electrons, the particles making up the metal, and any impurities in the metal. Therefore, more energy is going to be lost in these collisions (as heat).

        Furthermore, doubling the length of the wire will result in double the resistance. This is because by doubling the length of the wire one is also doubling the collisions that will occur, thus doubling the amount of energy lost in these collisions.

My independent research has found the following applicable information which explainf=ns the theory behind my prediction: -

“Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat. 

Join now!

The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) and the voltage across the wire (in parallel). These measurements are then applied to this formula:

 

V = I x R                 where V = Voltage, I = Current and R = Resistance

 

This can be rearranged to:

 

 R = V

        I

 

This prediction is also supported by Ohm’s Law, which states that the current through a metallic conductor (e.g. wire) at a constant temperature is proportional to the potential difference (voltage). Therefore V ...

This is a preview of the whole essay