Background Information Resistance of electrical current is all based around ohm’s law. R=V/I This is: resistance = potential difference / the current. I know that there are several different factors that affect the flow of electrons along a wire. These are: Cross-sectional area Length of wire Conductive material and Surrounding temperature I will now explain each in more detail. Cross-sectional area The larger the cross-sectional area of the wire the less resistance it has.
This is due to the larger spaces between atoms through out the wire allowing electrons to have a smaller amount of collisions with fixed particles therefore having a lower resistance. Length of wire When the length of the wire changes so does the resistance. The longer the wire is the more chances the electrons have to collide with a fixed atom reducing the flow. Therefore; the longer the wire the greater resistance. The Temperature The temperature of the wire and its surroundings has an affect because the higher the temperature the more energy the atoms in the wire have, they will move faster and through greater distances.
This leads to greater number of collisions with static particles producing a high resistance. Conductive material The material the wire is made of plays a great part in resisting the flow of electrons. Some conductive materials have a lower number of conductive electrons therefore having a greater resistance and also some materials naturally set up a greater resistance to the flow of the electrons. Preliminary Work For my preliminary work I am going to investigate how the current affects the potential difference across a filament bulb. Results.
After looking at these results I have found that the current and potential difference are not directly proportional to each other. This is because as the voltage increases the current increases at a different rate. This is due to the build up of heat in the bulb making the fixed particles more active setting up more collisions and a higher resistance. This has shown me that in my main investigation I will need to keep the current low in the circuit so that there is no build up of heat to affect the results. I have chosen to investigate the length of the wire to see how it affects the resistance for my main investigation.
Apparatus 1 length of wire (constantan 0. 31) over 1000mm 1 voltmeter 1 ammeter 1 rheostat (variable resister) 1 clamp stand 1 set of weights 2 crocodile clips 4 cells (batteries) 6 connecting wires Aim I want to find out the relationship between the length of the wire and the resistance of it. Method 1. Gather all equipment needed 2. Place out in correct order and assemble circuit 3. Connect the crocodile clips to the wire 200mm apart 4. Set the rheostat so that the voltmeter reads 3 V. 5. Read the ammeter and record the result. 6. Reset the crocodile clips to 400mm apart 7.
Reset the rheostat so the voltmeter reads 3V 8. Again record the result. 9. Repeat this process 3 times for each length (200mm, 400mm, 600mm, 800mm, 1000mm) Accuracy To make sure that the experiment is accurate I need to insure that I read the ammeter and voltmeter exactly and make sure that the 2 crocodile clips are correctly placed at the stated distance. Fair test To keep the experiment fair I need to eliminate all the other variables apart from the one I am going to investigate. To do this I will ensure I use the same wire so that the material and the cross-sectional area are the same.