1721 words - 7 pages

To investigate how the electrical resistance of a wire changes in relationship to its length.Physics Investigation Of ResistanceAim: to investigate how the electrical resistance of a wire changes in relationship to it´s length.Prediction: I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length. The graph to show this should therefore look something like this:Reason: with electricity, the property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. All metals are conductors and have an arrangement in similar form to this:As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. In fact resistance, in ohms(R) is equal to the electromotive force or potential difference, in volts (V) divided by the current, in amperes (I) - Ohm´s law.As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher. Resistance, in ohms (R) is also equal to the resistivity of the wire, in ohm-meters (ñ) multiplied by the length, in meters (l) divided by the cross sectional area, in square meters (A).The material and cross sectional area of the wire is constant throughout the experiment. Therefore it is clear from the formula that the resistance should be directly proportional to the length.Key factors: in this experiment we will only change one factor, the length of the wire. This should effect the resistance of the wire in the ways stated above.Fair test: in this experiment we are only changing one factor - the length of the wire, the factors that we are going to keep the same are as follows:We must keep the surrounding room temperature the same or the particles in the wire will move faster (if the temperature is increased) and this will therefore have an effect on the resistance.The cross sectional area of the wire must be kept constant throughout as well. This is shown in equation (2) where the cross sectional area is a factor that effects the resistance.The material of the wire must also be kept the same as different materials have different conductivity. The last two factors will be kept the same by using the same wire all...

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