To find how the resistance of a piece of wire depends on its length.

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Resistance Coursework

Aim: To find how the resistance of a piece of wire depends on its length.

Prediction: I predict that the length of the wire will effect the resistance by the longer it gets the resistance will increase.  I feel this will happen because the further apart the crocodile clips, in the circuit, then the further the electrons have to travel so the resistance will increase.  We did a preliminary experiment to find out the resistance of different wires.  In the experiment we kept the same length (60cm) and the resistances varied by a decimal point or stayed the same.  So from this I can predict that if you increase the length of the wire then the resistance will increase also.

Plan:

  1. Collect and set up apparatus like in the diagram above.

  2. Decide on length of wire between crocodile clips.  I decided on 10.0, 20.0, 30.0, 40.0,50.0, 60.0,70.0, 80.0, 90.0, 100.0, 110.0, 120.0 and 130.0cms.
  3. Take length set up circuit and turn on to take readings from Voltmeter and ammeter.
  4. With same length move to another position on wire and take readings.
  5. Move to third position on wire with same length and take readings.
  6. Now calculate average resistance using formula:                     R (resistance) = V (potential Difference) over I (amps)
  7. Take next length and follow instructions 3 to 6 for the rest of the lengths.

Fair Test: I plan to make it as fair as I can by keeping the circuit the same and so this would leave the connections the same so they wouldn’t change and the circuit will be the same for every reading.  I will also keep the thickness of the wire the same so the resistance didn’t change with the wire.  I could also use a stopwatch to take the readings at the same time.

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Safety: I feel that to make the experiment a safe one I will keep the crocodile clips upright so that they don’t touch anything else and short circuit.  Also I will only turn the circuit on when taking readings so that people don’t play and get electric shocks and so it doesn’t overheat.

Reliability: To make it reliable I will take each reading of the same length three times but try different positions, if the readings are very different I have done it wrong, if they are different by a decimal point then I can say they are reliable ...

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