How the Length of a Wire Affects Resistance

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Planning

The main aim of this investigation is to observe how the resistance is affected as the length of the wire in the circuit changes. The variable for this experiment will be the wire itself. I aim to find the resistance simply by changing the length of the wire where the voltage reading will be taken in parallel to the circuit. The voltage readings will be taken in parallel to the circuit where the variable piece of wire will be. This will eventually give the resistance of the variable piece of wire. The length will be steadily changed by 10cm each time. By finding the voltage of the variable piece of wire, and the current across the circuit will enable me to work out the resistance.

To get the most reliable results, everything else as part of the circuit and investigation must be controlled and kept constant. The type of material used in the experiment must be kept constant using the same material and preferably, exactly the same piece of wire. This must be kept constant because often different materials have different resistances. The type of material that will be used will be decided upon by preliminary tests that will be taken. The preliminary tests will involve using different materials as part of a test circuit. A similar circuit will also be used in the actual experiment. Another constant is the thickness of the wire. The thickness of a wire always affects resistance because the thicker the wire is, the lower the resistance will be. During the preliminary tests, the thickness of the wire will also be tested to see what sort of thickness is the most appropriate to use for the main investigation. Also, the number of equal cells used will remain constant. During the main investigation, the current across the circuit will be measured by an ammeter. Also the voltage in parallel to the circuit will be measured by a voltmeter. The resistance of the wire will be worked out by dividing the voltage by the current.

According to Ohm’s law, the resistance is equivalent to the voltage divided by the current; therefore I think that as the length of the wire increases the resistance of the wire will increase as well. This will be because atoms of all conductors have free electrons in their outer shell. Therefore, because of the structure of the atoms in all conductors, the electrons in the outer shell are able to move about freely. This is also true for a solid. When there is a voltage in parallel to the wire all of the free electrons are put in lines moving in the same direction forming an electrical current. When fixed particles in the wire collide with the current resistance occurs. When the resistance of a material increases the voltage must increase at the same time to “drive” the same amount of current. As the length of the wire is increased the number of collisions taking place in the wire increases so the resistance of the wire increases. Also, I think that the rate of resistance of the wire will be directly proportional to the length of the wire.

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To make the results as trustworthy as possible, I have decided to perform the experiment 3 times. The same process will be taken out 3 times and therefore the results will be more reliable. Also, I think that by working out the resistance to a total of two decimal places will provide more accurate results. To get these accurate results the voltage and current will have to be found to two decimal places as well, to ensure that the resistance is found to two decimal places. To keep this experiment as accurate as possible the length of the wire ...

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