Year 11 Physics Investigation- What factors affect the resistance of a wire?
We are trying to find out if the thickness of a wire affects the resistance of a wire and also how it will do that.
One reason I chose this investigation was because human reaction time is eliminated by not using the parachute method (the parachute experiment is to find out the factors affecting the rate of decent of a parachute), because you have to measure the timings on it by the eye and hand pressing the stop button and there could be some inaccuracies in this. In the test I am doing there is no space for human error because all the measuring is done by equipment and machines so all I ...view middle of the document...
We had the choice between length and thickness as our variable randomly because they were both very good to use as input variables.
Equipment Reasons why I chose it
Ammeter 0.05 amps precision to measure the amps in the experiment and it is easy to read and fast at measuring.
Voltmeter Precision of 0.2 volts when measuring the voltage, very easy to read and again fast at measuring.
Micrometer 0.01 millimetres precision when measuring the thickness of the wire, which is our input variable so it needs to be very accurate. The alternative to using this would be the ruler and we are not using that because it is a lot less accurate and precise.
Cell The reason we are using this is because it will supply the circuit with enough power to run properly with ease and no hassle whatsoever.
Connecting leads and crocodile clips These allow there to be something to measure. Allows electricity to flow smoothly around the circuit.
Set up the diagram as shown on the first page. Get your 5 wires and measure their thickness using a micrometer. Replace the place in the diagram where the resistor would be found with each of the wires and measure the results on the ammeter and the voltmeter and put the results into a table. Divide the voltage value by the current value to give the resistance of the wire, and add it to the table. Fill in the average resistance column by finding the mean value of resistance for each thickness of wire. The input variable I will be changing is the thickness of the wire. I will measure this using a micrometer. It is important to use a range of at least 5 values for the thickness of wire so that a clear trend can be identified from the results. The outcome variable will be the resistance of the wire, but it cannot be measured directly. To find the resistance of the wire, the voltage reading must be divided by the current reading for each thickness because R=V/I. There are a number of other variables i must control to ensure a fair test. I will talk about these one at a time.
Getting all the results in the same lesson ensures that the temperature is reasonably constant and will not affect the reliability of the results. If results were to be gathered on different days, the potential change in temperature would affect the outcome and it would therefore not be a fair test because the investigation is about how thickness of wire affects resistance. High temperature means higher resistance because the atoms vibrate, which means charges in the circuit are unable to flow through as easily than when the electrons are not vibrating.
The wires that are tested will be made out of the same material for every test. Some materials may be more resistant than others it would not be a fair test if we used different materials for each test.
The pieces of constantan wire will be the same...