I will be investigating the three factors, which affect the resistance in a wire. These are: > The length > The width > The material based on the conductivity. Temperature is also a factor of the resistance in the wire but more accurate apparatus will be needed to perform this, therefore I won’t be testing temperature. I will then be able to gain information see which properties produce the highest and lowest resistance. HYPOTHESIS From scientific knowledge I predict that the wires, which will give the highest resistance, are the longest wire, the thinnest wire and the most conductive material wire.
This also means that these would have the highest pd. as I/V= and if the resistance must increase the p. d needs to be higher to maintain this. If you were to imagine students trying to get through a corridor this could be compared to electrons flowing through a wire. The longer the corridor is the further someone will have to travel and the thinner it is the less freely students can travel through smoothly. Therefore the shortest wire the thickest wire and the least conductive material wire will have the least resistance.
Scientific knowledge has also told me that a good conducting material has more de-localising electrons than a poorer conductor therefore poorer a conductor the higher the resistance. Due to this I won’t be testing for copper as it is an extremely good conductor providing negligible resistance APPARATUS 1. 8 wires sellotaped to 8 rulers. 2. 8 crocodile clips 3. 1 power pack 4. 1 ammeter 5. 1 voltmeter METHOD I will set up my experiment as shown before beginning with the type of metal. My constant factors would be length (15cm) and thickness (26 swg) which I would be using for Constantine and Nichrome.
I will then switch the AC power pack on and record the P. D and current readings of each metal . After taking the P. D and current readings of the two metals I will test the thickness of the wire. My constant factors would be type of metal (Nichrome) and length (15cm). After recording exactly the same way I will test on length. My constant factors will be type of metal (Nichriome) and thickness (26swg). To change the length I will merely put the crocodile clips 5cm back each time, starting from 15cm. This experiment will be repeated two more times to check the accuracy of there results.
All results will be recorded in the results table. I will then calculate the resistance by using the equation, V/I = . These results will then be produced in a graph to show the relationship between P. D and current, and for any anomalies. All in all I will have 24 results altogether, 12 of potential difference and 12 of current. Safety Test To maintain safety I must ensure all basic precautions are carried out e. g. tying hair back. There could be a danger of hair touching the wire and if the wire does become TOO HOT the hair may get destroyed as well.