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Investigate how the electrical resistance of a wire is affected in relationship to its length.

Extracts from this document...


Current in A Wire Investigation

Aim:        To investigate how the electrical resistance of a wire is affected in relationship to its length.

Main Factors:






Ohms Law: (equation 1)

V  =  I  ×  R

Voltage  =  Current  ×  Resistance

  • Voltage is a measure of how much energy is transferred by a cell or supplied into each coulomb of charge.
  • Current is a flow of electric charge. The more charge that flows past a single point in a second, the higher the current.
  • The greater the resistance of a component, the smaller the current flowing through it for a given voltage. Resistance sloes down the current.

Pre-testing to inform the Plan

Planning our simple procedure:

Diagram of circuit


In this circuit the Ammeter will be placed in series and the Voltmeter in parallel to the resistor. We will place a length wire across a ruler leaving a small end free to connect to the circuit. The wire will be secured with celotape and crocodile clips placed at each end of the wire.    

We will fix either the current or voltage and then use ohms law to calculate the resistance.  The task is to find an appropriate voltage and current for different lengths of wire.


Constant Voltage or Constant Current?

We will do two small experiments to introduce the investigations. One where we will fix the voltage at 2.

...read more.




Detailed drawing of Ruler







                                Crocodile clip                Ruler measurements

During our experiment we must make certain that each time we record a result, that the crocodile clips are exactly inline with the ruler measurements. This ensures that the results we obtain are the accurate.


I think that as the length of the wire increases so to will the resistance, consequently decreasing the current. As the resistance of a material increases so must the force required to drive that same amount of current, therefore the rate at which the resistance of the wire increases will be directly proportional to the length.

i.e.        Double the length = Double the resistance

½ the length         = ½ the resistance

I think that the current will be inversely proportioned to length.

i.e.        Double the resistance = ½ the current

Detailed explanation of Prediction




                        path of electronsimage21.png

A longer piece of wire will generate a larger amount of interference between electrons and atoms, as shown above. This is because, the distance

...read more.


Solutions to inaccuracies

  1. To overcome the problem of the wire over heating there are a number of measures that we could have taken in order to prevent this from happening; We could have dismantled the circuit in between taking results as if it was disconnected there would be no flowing current and so would not over heat. Whilst taking our results we could have been quicker in making adjustments and the recording of our results, as this would have decreased the chance of producing a heating effect as the circuit would not be connected long enough. One practical suggestion would be to cover the wire in a type of waterproof material and then after each recording, it would be possible to place ice over the wire in order to cool it and reduce the effects of heating.
  1. In order to improve the precision of our results we could have tested a greater variety of lengths of wire, such as going up in 5cm steps as oppose to 10cm steps. We could also increase the overall length of our wire by taking the results up to 2 or 3 metres and, by hanging a weight on to one end of the wire we could ensure that all kinks and bends are smoothed out, leaving us with a more appropriate and exact piece of wire.

...read more.

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