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Investigate how the cross section of a wire affects the resistance in a circuit.

Extracts from this document...


Name: David Hayim Attias

Physics Coursework

Date: 6/11/03

To investigate how the cross section of a wire

affects the resistance in a circuit


In metals, when the electron becomes detached from the outer shell of their parent atom, it is then able to move freely between the positive ions of the metal, which arrange themselves in a regular lattice.

In pure metals, the structure can be represented like this:


The electrons are              

moving at a very high

speed randomly, with            

no pattern at all.  

image02.png= Positive ion

image03.png= Electron

The electrons in a pure metal move at a very fast speed randomly, with no pattern at all.

Metals are the best conductors because the detached electrons create a huge flow of ‘free’ electrons that can be made to move by the push from the voltage, in a circuit. Voltage is what gives the energy to the electrons, which pushes them along the wire of the circuit.


Metals are good conductors because their atoms are arranged in a regular lattice, so that when the electrons flow through them they have many straight paths to go through. If a positive ion collides with an electron, the electron will slow down and the positive ion will pick up some of its energy.

When this happens often, there will be two effects:

  1. The current will slow down.
  2. The metal will get hotter.  

When the metal gets hot it will cause the resistance to go higher. When the resistance increases, the current is reduced. Resistance stops current.

...read more.



My results have been clearly shown in these tables below. These tables show the voltage produced in each experiment, the current of each experiment and the resistance there is in each experiment. I know that my results are correct, because there are no figures that have come out wrong to disprove my theory. I have also drawn some graphs to prove that the voltage produced in a circuit is directly proportional to the resistance in the circuit. This graph was not hard to draw as the graph comes out to be a straight line. In the table there are different amounts of voltages because

...read more.



My experiments and investigation went very well. My results were very accurate as they all went up in proportion. But, there was a few experimental errors, but no result was off by a lot, but a few were off a little bit. I know this because when I drew my graphs I saw that the point didn’t fit in the straight or curved line. These errors could have been caused by:

  1. The voltmeter or ammeter was flickering therefore it was hard to get the exact reading.
  2. The wire could have mistakenly been measured a bit too long or too short.
  3. The wire could have heated up during the experiment, therefore getting a higher resistance.
  4. The wire may have had some kinks in it.

Due to all these experimental problems, reading the voltmeter, ammeter or the measurements of the wire makes my experiment not that reliable.    

As I had a few errors in my graphs I plotted another line using my graphical results to see if it would make a difference, if those results would be any better, but if you look at the graphs you can see that they are both practically the same, and the same points that are wrong in the calculated line, they are also wrong in the graphical line.


To prove my theory even further, I would repeat my experiment using:

  1. Different lengths of wires
  2. Test the wires at different temperatures
  3. Use a voltmeter and an ammeter which have a greater sensitivity

...read more.

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