Investigating (one of) the factors that affect resistance.
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Investigating (one of) the factors that affect resistance I am going to investigate how much changing the length of a wire affects the resistance in a circuit. I am going to test this by changing the length of a wire in a circuit, in steps of 10cm. I will record the readings of the volts and currents in a table. By recording these readings I am then able to work out the resistance. By using the formula. V R = I Safety precautions In order to avoid the dangers involved I will have to take safety precautions. In case the wire gets too hot I will place a heatproof mat under the wire during the experiment. Prediction Using my scientific knowledge on resistance I can make a prediction. I predict that the wires which measure 40cm and 50cm will have a low resistance respectively, because there is a shorter length for the current to travel. Meaning less collisions between the atoms of the wire and the electrons of the current. Also the electrons do not have to squeeze together for a long amount of time, because these lengths of wire are only short.
1 Ammeter- I chose this because we needed to accurately measure the amps in order to obtain the resistance. 5 Connection leads- I chose these because they were the easiest way to connect the circuit. Crocodile clips- I chose these in order to connect the apparatus together in the circuit. 1 meter of wire- I chose this because it was the fairest way to test for resistance. Variables The independent variable is the resistance of the wire. The dependant variable is the length of the wire. The controlled variables are the potential difference, the power pack, the voltmeter, the ammeter, the piece of wire used, the temperature. The only variable I am going to change is the length of the wire. I must keep all the other variables constant. If I did not then just one small change could completely change the outcome. Obtaining In order to carry out a fair and reliable test I repeated the experiment three times and then I used the mean to calculate the resistance. I decided to use readings starting from 10cm and then work upwards at a 10cm pace.
This can be elaborated on by explaining the reasons why the resistance in a wire goes up as the length increases. Evaluating Our experiment did not as well as we had expected. As you can see from our graph some of our results were repetitive and were anomalous. This was because we did not use our voltmeter/ammeter to the correct degree of accuracy. Thus our results had to be rounded, leaving many of them the same, thus leaving us with anomalous results. If we were to repeat our experiment again we could use a more precise voltmeter/ammeter such as a digital one, this would give us a more precise graph. But because we used a non-digital piece of apparatus we found it harder to obtain accurate results; mainly due to having rounded to two significant figures only. Also having the first result at 1.2 amps we were not able to set the scale to 1amps. Instead we had to set the ammeter to a less accurate scale of 5amps. However our experimental results are good enough to support our prediction and conclusion as they follow the line of best fit. However to improve our experiment we could use a digital ammeter/ voltmeter in order to obtain better results. Caroline Morris Physics Coursework
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