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What Factors Affect the Resistance In a piece of wire?

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What Factors Affect the Resistance

In a piece of wire?


  Electric current traveling through a piece of wire is a flow of free electrons. As electrons are negative they travel from the negative terminal to the positive terminal as opposite charges attract and like charges repel. This means they are pushed from the negative terminal and attracted back to the positive terminal.

  As the free electrons flow round the circuit, they collide with the vibrating atoms in the wire it is traveling through.


  As the electrons hit the vibrating atoms they give off some of their kinetic energy and slow down. This is how current is resisted.


Temperature: As temperature increases the resistance in the wire will increase. This is because when the wire is heated up, the atoms in the wire are given more energy and so vibrate much more and much faster. This means that the free electrons flowing around the circuit will collide more with these atoms and will lose some of their kinetic energy, therefore resisting the current more.

Diameter of wire: The smaller the width the smaller the resistance. This is because an a thicker piece of wire there are more atoms for the free

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Ωs setting.

4) Record the Ωs reading.

5) Move the 2nd crocodile clip 20cm away from the 1st clip and record the Ωs reading again.

6) Record the Ωs reading when the 2nd clip is 30, 40, 50, 60, 70, 80, 90, 100cm away from the 1st clip on the wire.

7) Repeat the experiment twice more to make the results more reliable.

8) Using the formulae:

                                      Resistance = Voltage


  Work out the resistance at the wire at each length. Then take an average resistance reading by adding the three results and dividing the total by three.

Safety: Do not put the crocodile clips too close together or the circuit will short circuit.

  To ensure a fair test the circuit leads must stay the same throughout, because these add resistance themselves. If the lead was changed for a longer lead more resistance would be added make the results unreliable.

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Ω away from the best fit line; these were at 80cm and 100cm these may have been slightly wrong due to the bad connection.

  Also the wire that I was measuring became twisted so that the length of the wire may have been slightly wrong. Another criticism is that when the wire was short it became hot this may have caused the resistance to increase so it would not be very accurate. This meant that the experiment is limited to longer lengths of wire.

  To make this experiment more reliable I would have to take even more check readings to ensure consistency and find another way of connecting the wire up. My results were reliable as the check readings were consistent almost through out my results.

  My results show that resistance increases with length proportionally, but that may only be true for my wire so my conclusion may be wrong for other wires so it would be necessary to test some other wires to know that my conclusion is correct for all wires. Also it may be useful to test the other input variables such as width and the temperature.


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