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How does the length of wire affect resistance?

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Elizabeth Stephens 11N Physics Coursework How does the length of wire affect resistance? Aim To find out how changing the length of wire will affect the level of resistance when current flows through it. What is Resistance? Current is a flow of electrons. As they travel down a wire there is a force acting against them, this is Resistance. Resistance is caused by two factors even 1. Positive nuclei in the wire. The positive nuclei attract the negative electrons and deflect them from travelling in a straight line. This means the electrons travel a much larger distance to go the same length through the wire and take longer. 2. The vibration of the positive nuclei in the wire. The positive nuclei vibrate at any temperature above absolute zero. The vibrations mean the nuclei move around and this causes more frequent deflections. This makes the journey of the electrons slower. The longer the wire, the higher the resistance because there are more nuclei in the way. The higher the temperature the higher the resistance because the nuclei have the energy to vibrate more and therefore cause more deflections. The larger the cross section of the wire the lower the resistance because more electrons can pass through the wire in the same amount of time. ...read more.


I have two thicknesses of wire, 0.19mm and 0.56mm. I want to use the wire that has the highest resistance as the results will be easier to record. This should be the thin wire as the thinner the wire is the higher the resistance because less electrons can get through in the same amount of time. I shall test this to make sure that I am correct. Cross sectional area of wire Resistance at 10cm Resistance at 20cm 0.19 6.3 9.0 0.56 2.6 3.3 My preliminary work shows that I should use the thinner wire as there is the greatest resistance change and therefore less error in my measurements. Results 1 Length of wire (cm) Resistance (ohms) 1 2 3 Average Rounded for graph 10 1.3 1.3 1.2 1.2666666667 1.3 20 2.6 2.4 2.4 2.533333333 2.5 30 3.7 3.6 3.6 3.6666666667 3.7 40 4.8 4.8 4.8 4.83 4.8 50 6.2 6.1 5.9 6.066666667 6.1 60 7.5 7.3 7.2 7.3 7.3 70 8.5 8.5 8.4 8.467 8.5 80 10.0 9.6 9.5 9.7 9.7 90 10.9 10.9 10.8 10.866666667 10.9 100 12.0 12.2 12.0 12.0666666667 12.1 Results 2 Length of wire (cm) Voltage (V) (Volts) Current (I) ...read more.


Using computer technology to measure the thickness and length of the wire would have also made a difference to the accuracy although I think that this experiment was very accurate in measurements. The evidence I have collected is sufficient to support my conclusion as I have investigated the theory in three different ways and they have all followed the same trend of being proportional with very little difference between the results of each experiment. Each experiment has ten different measurements which allow me to plot a fairly accurate graph and I have repeated each measurement three times (except results 3 where this was not appropriate) to calculate an average for the graph which makes the experiment more accurate. If I had more time I could make my experiment more accurate by accounting for the effects of temperature on results 2. To do this I could either: * Set up diagram 2 with 100cm of wire and measure the temperature of the wire. I would keep the current switched on and at regular temperature intervals I would measure the resistance to find out how much it increases so that I could find out whether that would have affected my results significantly. * Or I could use the formula R = H to calculate the I2 resistance with different temperatures and a set current. (H = heat) ...read more.

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