Physics Coursework Plan: The Resistance of a Wire

Resistance (in ohms) = Voltage across the resistor* (in Volts)

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                                       Current through the resistor* (in Amps)  

*In this case the wire that is being tested replaces the resistor in the equation

Also I will change the temperature of the wire with a Bunsen burner to see how temperature of the wire has any affect on the resistance . There will be a set of main components that will be used in both experiments. Now I will explain how they will be used to give effective results. The most important part of the equipment is the system of measuring which is used. A multimeter that measures volts, amps and ohms as well as other units will be used and will be set to the appropriate mode to measure the right unit and scale. A voltmeter will be connected in parallel to the wire so that it can measure the voltage effectively. The ammeter will be placed in series before the wire so that it also will measure effectively.

Next is the wire itself. The wire will be measured at different length so I have chosen to use a scale of 2 – 20cm in length, as I believe that if the wire is too long or short the results will not be accurate. It is notable that a resistor is just a coiled up length of wire. Usually the trend with resistors is that the longer the wire is the larger the resistance is. Also the material of the wire will differ. I have chosen 5 different materials of wire because that is a reasonable amount to give a variation of results, which can be recorded. The next thing that might affect the resistance of the wire is the width. The width will be measured and as many different thicknesses will be used as possible. Also the temperature of the wire can we varied to see if the temperature would change the resistance.

In theory the resistance of wire depending on its length should get larger as the wire gets longer. However as there is more vibrating ions in a wire that is longer to hamper the electric flow, there are also more free electrons so the effects should cancel each other out. The resistance is proportional to the length of the wire so if the length of the wire doubles the resistance should double. Even so at constant voltage, less energy is free to the electrons to move through the wire so the electrons move more slowly around the circuit. Therefore the resistance will get higher. The temperature can affect the resistance because when a material reaches a certain temperature called its critical temperature the material no longer gives any resistance to the electrical flow.  The width of the wire can also change the resistance. This is because there are more free electrons and less energy can  be given to the electrons through each centimetre of wire. In turn the electrons move slower around the circuit causing the resistance to rise.