Based on my scientific knowledge, I feel that the shorter the length of wire, the less resistance there will be, and vice-versa – the longer the length of wire then the more resistance there will be. I have based this prediction on the knowledge that when the wire increase in length, the more current will be required, therefore decreasing the current and increasing the resistance. Another reason for my prediction is that when electrons are in the circuit, they are forever losing energy. While going through a longer wire and longer circuit then the electrons will lose energy and more will be sent, creating yet more resistance.
I hope my graph for the experiment to look like this: I also carried out a run-through of the test in a preliminary investigation and I found that the resistance does increase with the length of wire. This is probably due to what I have said in the above part of my prediction, however, it is the main test’s data that I will be using and I will establish the accuracy of my prediction later in my conclusion and evaluation..
SAFETY Safety is an important factor in this test in that if used in the incorrect way then electricity can kill.SO: I will not touch sockets and the power supply unit (PSU) with wet hands. I will use a low voltage – too high a voltage will melt the wire and damage equipment. FAIR TEST To make the test fair I will only change one variable, that being the length of the wire. I will use the same length of wire each time and same components. I am going to put the PSU on 6 volts – a safe voltage, relating to safety, from preliminary, 8 volts was too high and began to melt the wire on some tests and will use 0. 25mm nichrome wire.
I have a range of 10 measurements – from 10cm to 100cm at regular 10cm intervals, 10 is an easy number to take averages with and will give me enough data to obtain a fairly accurate result; I will test each length of wire 3 times and take an average. EQUIPMENT ; DIAGRAM CHANGES FROM TRIAL EXPERIMENT While trialling the experiment I felt that the following changes needed to be made: Measure at 10 regular intervals instead of the original 5 – it will ensure that I will get a better average. Use sellotape to stick wire to ruler – stop wire become twisted and keep it straight on the ruler.
For the shorter lengths of wire, the power pack must only be on for a matter of seconds, due to the lack of wire needing to get through, the particles will build up and melt the wire. METHOD Measure a piece of 0. 25mm nichrome wire to 100cm Connect all components together using crocodile clips Attach the wire to the ruler, using Sellotape. Switch the power unit onto 6 volts and onto a direct current, I only want the current to be flowing one way and not alternating. Measure 10cm on the ruler, turn the P. S. U. on and take the reading on the ammeter and voltmeter. I will do the same for 20cm, 30cm, 40cm etc.