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Planning Experimental Procedures

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Planning Experimental Procedures Introduction In this experiment I will make a circuit using different materials of wires. To alter the length of the wire to be tested I will use crocodile clips. Voltage will be measured by using a voltmeter. Amps will be measured using an ammeter. Then the resistance is to be calculated. Key Factors Identified One variable should be carried out at a time, to make it a fair test. I am going to investigate what factors affect the resistance of a wire. Here are the main factors, which affect the resistance of a wire and some reasons as to why they affect the resistance of a wire: The material of the wire (What the wire is made out of) The length of the wire The thickness of the wire (The diameter of the wire) Temperature of wires Contact resistance The material of the wire The material of the wire is important because different metals have different properties. Metals, as wires are different because copper is very good at conducting electricity, if you had very large lengths of copper wire then you would be able to see the resistance change. Electrons find it easier to pass through some materials then others. I am going to use nichrome, copper, manganin and Constantan. The material of the wire when cut should be clearly labelled to prevent it from being mistaken as another material. The length of the wire The length will make a difference because when you have a long wire the electrons have to squeeze together to be able to pass through the wire than they do to be able to pass through a short wire. The longer the wire the longer the current has to travel so each electron is more likely to collide with the other electrons, slowing them down, causing heat to be produced. When cutting the wire, use a ruler and be as accurate as possible. ...read more.


Average Current (Amps) Potential Difference Average (Volts) Resistance (Ohms) ? 5 0.6 0.06 0.1 10 0.5 0.1 0.2 15 0.55 0.15 0.27 20 0.53 0.2 0.37 25 0.54 0.25 0.46 30 0.5 0.4 0.8 35 0.5 0.3 0.6 40 0.49 0.44 0.89 45 0.5 0.45 0.9 50 0.48 0.49 1.02 Here is a step by step plan of how I recorded my results, 1. I recorded the readings from the analogue ammeter 3 times. 2. I found the analogue average, by adding the 3 results and dividing by 3. 3. I recorded the readings from the digital ammeter 3 times. 4. I found the digital average, by adding the 3 results and dividing by 3. 5. I added the digital and analogue ammeter together and divided by 2 to find the amp average. 6. I recorded the volt meter readings 3 times 7. I found the average of volts. 8. I divided the amp average by the volt average to give me the resistance in Ohms. 9. I swapped my results with another group so that I could later compare the results in my write up. There aren't many anomalous results. I have circled the anomalous results. I followed this step plan for recording results for 24 SWG of Manganin, Constantan, and Nichrome. The secondary data only has the average numbers because I do not need to have every single recording of the other person's data, I have enough information because I have their averages. Precision I attempted to be as accurate as possible as I said in my previous precision. I was being accurate by... * When I measured the wires to test their resistance I used a ruler to be correct in measuring, then I asked a member of my group to double check the length of the wire to see if I was correct in measuring. * Once the wires had been cut to save confusion I labelled them with their SWG, length and material of wire. ...read more.


I think that going up in 2.5 cm's is a suitable range because it is half of the previous range that I had which was 5 cm. Suggest how you could extend your enquiry into other areas There are many way of extending this experiment... I could have used different SWG wires as well as 24 SWG. I could have found out why the resistance changes as I increase/decrease the SWG. I could have had a different amount of voltage (DC) going around the circuit, I could investigate what happens as I increase/decrease the voltage. I could use other materials other than copper, manganin, Constantan and Nichrome. I could have used gold, which has a very small resistance because it is a good conductor. Instead of changing the length by increasing it by 5 each time I could repeat the same experiment but going up in 2.5's instead of 5's. But if I did have another chance to repeat this experiment then I would conduct this experiment in a fridge so that the heat made from the clashing electrons will immediately be lost before they can have any effect on the electrons. I could have researched into contact resistance. I could have found out how much the resistance is changed if there is more/less contact around the circuit. This diagram is an example of contact resistance. In the experiment I used crocodile clips, but if used a razor blade or something similar amp and volt reading could be different, and that would make the resistance different. This diagram show the grey crocodile clips representing the crocodile clips, which have a larger surface area contacting the actual wire, and the larger the surface area, the larger the resistance. However if the conductors with small surface areas were used i.e. the razor sharp blades, then the resistance could have been less. The resistively of the metal of the crocodile clip is another factor to investigate into. ?? ?? ?? ?? Science Coursework-Physics Chandni Ladva ...read more.

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