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Resistance Investigation

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Georg Simon Ohm (1789 - 1854) In this investigation we will test different lengths and widths of wires and observe and record the resistance. We will do this investigation in a group of four people. We will then see how these variables affect the resistance, and which length or with will give the lowest resistance and which gives the highest resistance. We will vary the length of the wire we use in my preliminary experiment. There are a number of different factors that may influence the resistance of a wire. These include the material, length, diameter, cross sectional area, and temperature. In our investigation we will mainly focus on the affection of the diameter and the cross sectional area. Scientific background Georg Ohm gave his complete theory about electricity in 1827, which includes the theory of the resistance of wires, known as Ohm's Law. The German physicist Georg Simon Ohm was born in 1787 (not sure whether 1787 or 1789) in Erlangen, Germany. His parents were not well educated but his father was a man who educated himself and was therefore able to give his son an excellent education. In 1805, Ohm started his teaching at the University of Erlangen. He taught mathematics at several schools and wrote the elementary geometry book. ...read more.


We will be using six wires with different thicknesses, which will be 22, 24, 26, 28, 30, and 32 SWG. As each wire is labelled with this code, we do not have to calculate the diameter, because they are already measured. It is very important in this investigation to try to keep an as constant temperature as possible, so it does not affect the resistance. If the temperatures of the wires increase rapidly, this could lead to illusions in our results and analysing, because too hot wires will increase the resistance. In our preliminary experiment we noticed that the same wire with different currents caused the temperature of the wire to increase thus affecting the resistance. We found out that if the current increases, the wires get too hot very quickly. Therefore we decided to leave the current at 0.2 A for our main experiment, because we did not want the temperature change to occur as we are investigating the length of wires and not the temperature. The circuit diagram below shows how we are going to set up our electric circuit. Prediction From own scientific knowledge and a bit of research I know that the resistance increases if the resistor (in this case the wire) ...read more.


Diameters (in millimetres) Length 0.71 0.56 0.45 0.38 0.31 0.27 10 cm 0.33 0.56 0.86 1.29 1.78 2.13 20 cm 0.60 1.03 1.55 2.34 3.38 4.00 30 cm 0.90 1.51 2.44 3.36 4.88 6.08 40 cm 0.56 2.00 3.04 4.50 6.64 8.40 50 cm 1.51 2.56 4.00 5.70 8.19 10.18 60 cm 1.76 3.09 4.85 7.08 9.83 11.87 70 cm 2.08 3.42 5.29 8.14 10.71 14.08 80 cm 2.37 4.53 6.72 9.63 12.27 16.73 90 cm 2.65 4.31 6.88 10.17 14.62 18.60 100 cm 2.96 4.79 7.57 11.69 19.50 19.50 By doing this investigation we found out that different thicknesses of wires and different lengths have also different resistances. The numbers, labelling each graph are its diameter, in order to compare its thickness to other wires. It is given in millimetres. As you can see the wire with the wire with the diameter 0.27 mm has the highest resistance. The scatter graph above also shows that the thickest wire, which has a diameter of 0.71 mm, has the lowest resistance. By using these two examples we can see one trend in the diameter: The thicker a wire is, the less resistance it has. 1 I = current (Amps); V = voltage (Volts); R = resistance (Ohm, ?) ?? ?? ?? ?? Kamran Adnan (11 S2) Resistance Investigation Page | 1 ...read more.

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