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The aim of this investigation is to find out how the resistance of a wire changes when a variable is changed.

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Introduction

Resistance of a wire investigation By Seb Jenner 4/1/03 The aim of this investigation is to find out how the resistance of a wire changes when a variable is changed. The variable that I have chosen is the length of the wire. My preliminary experiment showed me that the best wire to use out of the three provided, was Constantan, this was because we found that it was a poor conductor, unlike copper, and therefore it's resistance is large and easy to read. We can not do cross section of a wire because we don't have enough range so it would have been inaccurate. Ohm's law states that provided the temperature of a conductor remains constant the potential difference across it is directly proportional to the current through it. We can calculate the resistance of something with this equation: R = V ? I (Resistance = potential difference/voltage ? current) The variables that I could have chosen were: Wire length: If the length of the wire is increased then the resistance will increase. This is due to the electrons having a longer distance to travel, which means that more collisions will occur. ...read more.

Middle

And creating more collisions between them. I predict that when I increase the length of wire the resistance will increase, this is because the electrons have a greater distance to travel therefore it will take them longer to reach the other end of the wire. More collisions between the electrons will also occur because of the more time they will spend travelling, this will also slow them down. I also believe that the resistance will be directly proportional to the length of the wire. The apparatus that I shall need is: 2 crocodile clips - to clip the connecting wires to the constantan wire 100cm constantan wire 1m ruler - to measure the length of the wire Multimeter - to measure the ohm's 2 connecting wires - to connect the crocodile clips to the multimeter. Method * First I shall collect all my apparatus (listed above) * Then I shall plug the connecting wires into the crocodile clips and the multimeter. * The first crocodile clip shall be placed at 0cm. * The second shall be placed at 10cm. ...read more.

Conclusion

1.9 30 2.6 40 3.7 50 4.2 60 5.2 70 5.9 80 6.5 90 7.4 100 8.4 I had no anomalous results and my results did not change at all which is a good sign that my readings were accurate. My results show that my prediction was correct. And that the resistance of the wire is proportional to the length. I have shown that when the length of a wire is increased the resistance increases. I believe that this is because the electrons have a greater distance to travel therefore it will take them longer to reach the other end of the wire. And more collisions must have occurred between the electrons, this would also have increased the resistance. I believe that overall my results were quite accurate, this can be seen by the line of my graph, as it goes very straight and does not waver. The inaccuracies may be due to my measuring as you can not rely on just your eyes and a metre rule to measure accurately, but it was the best that I could achieve. The metre rule is only accurate to 1mm and the multimeter is only accurate to 0.01 ohm's. ...read more.

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