Investigating Resistance's of Wires

Investigating Resistance's of Wires
Investigating Resistance?s of Wires Aim: To investigate different resistances of wires to see which has the most resistance and which shows the least resistance. I will be looking at resistances affected by the length of wire. Variables I could change: I had the choice of several variables to change such as length, cross sectional area, material and temperature the experiment is conducted at. Prediction: I believe that by increasing the wire?s length it would increase the resistance. Therefor by decreasing the length it would also decrease the resistance. I also believe that the rate of the increasing resistance will be directly proportional to the length so if the length were doubled the resistance would also double. I think the graph will look like this: Reason: The property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. (Information found on a gcse Physics website) Ohm?s law: In1826 Georg Ohm discovered that the current flowing through the wire is proportional to the potential difference across it (providing the temperature stays the same.) ?Proportional? means if you double the potential difference the current is doubled (this information was found in gcse Physics for you text book) Current through the wire
Resistance, in ohms? is equal to the electromotive force or potential difference, in volts (V) divided by the current, in amperes (I). Variables effects: By increasing the cross sectional area I believe there will be less resistance because there will be more atoms inside the wire. The way to explain this is to imagine a water pipe, the thicker the pipe the more water can flow through it the thinner it is the less water that can flow through it, this is just like the energy flowing through the wire. The substance will vary the resistance differently depending on whether it is a good conductor or not. Copper would have a low resistance, as it is a good conductor. Whereas Nicrome, which is used in heating elements, is a bad conductor, as all the atoms inside it are different sizes which makes it harder for the electrons to move through the wire, resulting in more resistance. You could also vary the temperature that would, as the temperature increases, increase the resistance because heat causes the atoms to vibrate more which makes it more difficult for electrons to move through the wire as they are regularly obstructed. Increasing and decreasing the length, as I will do, will vary the resistance. Increasing the length will increase the resistance, as there are more atoms for the electrons to move through. Doubling the length will double the amount of atoms there for double the resistance. Why use length as my variable: I will be looking at the length of the wire, as this will be the easiest to conduct and be easiest to collect results to complete points for plotting a graph of results. Fair test: I will need constants and inconstant which will be length. We will need the constants to make sure that the experiment is always the same for fair results. Constants Inconstant Cross sectional area of wire Length Wire material Where everything is in the circuit Same apparatus Same current Temperature conducted in If the cross sectional area of the wire were changed this would effect the results, as there would be more atoms in the wire that would cause there to be less resistance. The wire material would effect the results depending on the conductivity of the wire; some metals would cause more resistance, others less resistance. The change of temperature would cause the atoms to vibrate more affecting the results by showing more resistance. The current must also be kept the same, as this will affect the readings making it more difficult to be able to plot a results graph. It will also affect the temperature of the wire if the current is too high, making the resistance higher and may also melt the wire. Apparatus: ? Powerpack set at 4 Amps. (found from trial run that this is fine) ? 5 connector leads ? 2 crocodile clips ? Voltmeter ? Ammeter ? Wire Crocodile clip [image] [image] Voltmeter [image] [image] Ammeter [image] [image] 100cm of 28 swg (diameter 0.40 mm) wire [image] Power pack [image][image] [image] [image] I will be using a power pack to control the volts sent through the circuit that will be measured and recorded using a Voltmeter through the wire. The wire will be varied in length started using at 1m in between the crocodile clips, for a fair test, and then the crocodile clips moved to the appropriate place, the measurements will depend on my trial run. The Voltmeter measures the power going through the wire and is set in parallel series to show the volts going through the circuit before and straight after it has gone through the wire. The crocodile clips are used to join the wire into the circuit and for the Voltmeter to be connected to. The ammeter is used to measure current and it does not matter where this is placed in the circuit. The voltmeter is set parallel to the wire as then it takes an accurate reading. It needs readings before the wire and directly after the wire to measure the resistance the wire causes in the circuit. Plan: I will firstly conduct a trial run, but this will use the same plan as my actual experiment as long as it works ok. 1. Set up as shown above (constant set up) 2. Set power pack to 4V (constant) but leave pack off 3. Measure 1m of wire (constant) and clip the wire so in between the clips is 1m of wire 4. Turn on the power pack and take readings from both the Ammeter and the volt meter 5. Turn the pack off and back on take another reading and then repeat, so you end up with 3 results for one length 6. Take the wire and measure out the next distance (for my trial run this will be 50cm) 7. Repeat steps 4 and 5 for each length you wish to record Trial run results: The run was carried out using 4V and the set up as shown, with all the same constants as will be used for the actual one. Volts Amps Resistance 100cm 2.01 0.40 5.03 40cm 1.76 0.89 1.98 These results show me that 4V was ok to use as the wire didn?t get too hot and we still got an appropriate reading. From these results I have decided to use the wire at lengths 100cm, 90cm, 80cm, 70cm, 60cm and 50cm. I chose these measurements, as there was such a large difference for the trial run that I think a difference of 10cm each time will make a considerable difference in the resistance. My preliminary work showed me that my previous plan would be fine to conduct. Range of values to be used: I have chosen to use 6 values to give me more points to plot on my graph for more accurate results. I have chosen to use 100cm, 90cm, 80cm, 70cm, 60cm and 50cm. I have chosen to use these values as we are given 100cm of wire and use 6 values. I chose to go down in 10cm other wise the wire would go too short, this would be dangerous because the wire would get too hot and melt. I will be using 4V as this worked with my trial run that went down to 50cm at 4V and the wire was fine. Safety: The main thing about this research experiment will be making sure the wire does not melt. The wire may melt: ? If the wire is too short it will become too hot and may melt ? If the voltage is too high the temperature of the wire will increase effect one of the constants of the experiment and melt the wire I will have to make sure my hands are dry while using electricity and make sure I don?t touch the wire at any time, as it may be hot. This is not a dangerous experiment but you must always handle electricity with care. Accuracy: The experiment needs to be accurate for they?re to be fair results. I will make sure tests are fair by: 1. Making sure that the wire is accurately measured from the inside edge of the crocodile clips 2. Make sure the wire is always straight 3. The reading should be done promptly when the circuit has electricity flowing through it and should be accurately read. 4. Make sure the tests are done the same way each time using the same apparatus 5. Keep the timing the same on 5 seconds to record turn off, 2 seconds turn on 5 seconds to record, etc. for each length, 6. The tests will be done 3 times for each length. Results: Any results are rounded to 2 decimal places 100cm Volts Amps Resistance 1st 1.75 0.38 4.61 2nd 1.76 0.39 4.51 3rd 1.75 0.38 4.61 [image] Overall resistance 4.58 1st, 2nd and 3rd results added and divided by 3 (average) 90cm Volts Amps Resistance 1st 1.69 0.41 4.12 2nd 1.69 0.41 4.12 3rd 1.70 0.42 4.05 Overall resistance 4.10 80cm Volts Amps Resistance 1st 1.65 0.45 3.67 2nd 1.65 0.45 3.67 3rd 1.65 0.44 3.75 Overall resistance 3.70 70cm Volts Amps Resistance 1st 1.55 0.49 3.16 2nd 1.56 0.48 3.25 3rd 1.56 0.49 3.18 Overall resistance 3.20 60cm Volts Amps Resistance 1st 1.69 0.62 2.73 2nd 1.70 0.63 2.70 3rd 1.71 0.62 2.76 Overall resistance 2.73 50cm Volts Amps Resistance 1st 1.63 0.69 2.36 2nd 1.63 0.69 2.36 3rd 1.64 0.70 2.34 Overall resistance 2.35 [image] I had no anomalies in my results. Trends: From the graph we can see that as the length of the wire increases so does the resistance. The increase is constant, as there is a straight line. Conclusion: From my results I can see that my prediction was roughly right. The resistance didn?t exactly double as the length doubled but it did roughly. But the resistance did change in proportion to the wire length. My predicted graph looked the same as my final result?s graph. The graph showed that as the length increased so did the electrons that made up the current had more fixed particles in the wire to pass through which caused more resistance due to more collisions. Evaluation: I believe my results are quite reliable as I stuck to the commented ways to make sure this test was fair and safe. I kept the constants constant and the inconstant where changed appropriately as described before test was undergone. We can see that the results where accurate as the graph shows a straight line with no anomalies. There may have been some errors encountered in the measuring of the wire as it was almost impossible to hold the wire straight measure it against the ruler then fix the crocodile clips in exactly the right place. One of our crocodile clips was not particularly strong and could have easily moved to change the length. It was not easy to control the length and at several points this may have been changed. Overall I think my experiment was quite successful, with successful results conducted in a safe and controlled condition. The graph showed no major anomalies and there where no obvious problems while conducting the experiment. A lot of information I have used in my AT1 has been from notes on a gcse Physics website. There is also some information from the Physics for you book.

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