I think these lengths of wire is suitable for the experiment. 10 lengths is good enough to show us a general pattern. Equipment- -Ammeter -A 1m ruler (to measure length of wire) -At least 8 electrical cables -Voltmeter -Power Supply unit -at least 600cm of Constantan -crocodile clips Method- 1. Connect the electrical circuit as shown in the preliminary work. Make sure all the wires all connected correctly. Note that the voltmeter has to be connected in parallel because it has a very high resistance, current will not be able to go through. 2.
Before doing anything else, set the voltage of the power supply unit to 0V. Then turn on the power Supply unit (PSU). 3. Connect the piece of wire of desired length to the two crocodile clips (both ends) 4. Now set the PSU dial to 2. Turn on the Machine. Allow readings to settle then record readings from the ammeter and the voltmeter. 5. Turn of Machine. (avoid the wire getting hot) 6. Do the same adjusting the dial switched to 2, 4 and 6. Change the lengths of the wire each time using the following lengths- 20, 40 60, 80,100, 120,140,160,180,200cm. Record the readings from the ammeter and the voltmeter. 7.
Once you have finished all the experiments you have to divide the volts by the current (amps) to find out the resistance. It is explained how to do this in the analysis later. Analysis Analyzing the Graph- From the pattern on the graph, we can tell that my prediction was correct. An increase of length gives you an increase in resistance. This can be seen because the line of best fit is moving upwards while the length of wire is increased. All the points on the graph are almost on the line of best fit, it was very easy to draw the line of best fit. There were one or two points that did not fit the line completely.
These were the last two lengths. 180 and 200cm. This could have happened due to some experimental errors. The graph proves that as the length of the wire increases the resistance of the wire increases proportionally. This means that if we double the length of the wire we also double the resistance. How I calculated the results- Resistance = Voltage / Current So for example: Voltage = 0. 51V, current = 0. 15A. Therefore resistance = 0. 51 / 0. 15 = 3. 95? I then averaged all the results (readings on the dial 2, 4 and 6) to come up with a final pair of results which used to plot on the graph.
Conclusion- From the graph we can tell that almost all the points are on the line of best fit. The length of wire and the resistance is directly proportion to each other, as in they rise together. If we double the length of the wire the resistance will too double. This proves that the resistance of the wire will vary according to the length and width of a wire. The longer the wire the higher the resistance. The length of the wire and the resistance rise together. The increase in voltage is increasing the amount of energy transferred every second in the circuit.
My theory is, if length of the wire increases, there is less chance for the electrons to go through. Most of them bump into the atoms inside the piece of wire, therefore increases resistance. According to my graph my prediction was correct; a rise in length is a rise in resistance. Evaluation Problems encountered- The problems encountered were very mild except for when we were taking measurements for small lengths of wire. The wire got very hot; it was difficult to take readings because the readings on the meters kept on changing in high ranges. How accurate were my results-
My results may not have been extremely accurate however when we draw the line of best fit we can see the pattern quite clearly. It is good enough for us to find and interpret a pattern from the line of best fit. The ruler we used may not have been entirely accurate. Also, the voltmeter and the ammeter is limited to 2 decimal places, and are not entirely stable (the readings are always changing). We can only measure an approximate reading. How ever as I said earlier I feel my results are good enough to show us a general idea of what is happening. Comment of the overall experiment-
Overall, I feel that the experiment was done in a quite good state. Yes there were 1 or 2 anomalous results; however the line of best fit still turned out as expected. 10 results is good enough for us to draw a decent and accurate line. All in all most points lie very closely to the line of best fit. The line is quite reliable as it turned out as expected (i. e. it matches my prediction) and it also matches the research I had done previously. It shows us a general pattern of the length of wire and resistance being proportional. Things I could have done better- The experiment could have been done much more accurately.
I could have used a more reliable ammeter and voltmeter so readings can be more accurate, they can be more stable and corrected to more decimal places, in this case there will be fewer errors in the graph. We could also have used fewer wires. The wires we use have a very slight resistance, therefore affecting the experiment slightly. Besides all this there is not much else we could have done. The experiment could have turned out better if the equipment used was much more advanced (explained above). However as said earlier the results are good enough to show me a general pattern and allow me to analyse what happens.