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Investigating how thickness and length affect the resistance of a wire.

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Investigating how thickness and length

Affect the resistance of a wire


 I plan to investigate how the length and thickness of a wire affects the resistance.  I plan to do this by keeping the voltage the same by using a variable resistor and measure the current when varied lengths and thicknesses of wire is in a circuit


There are a few factors that can affect the resistance.  These are;

image00.png        Temperature

image00.png        Thickness

image00.png        Length

image00.png        Material

        I plan to change the length of nichrome wire at intervals of 10cm’s.  I also plan to investigate how the thickness of a wire affects the resistance.  I plan to do this by measuring different lengths and both thicknesses of wire and comparing results.  In my experiment, the voltage, material and temperature will remain constant.


I predict that the longer the wire is the more resistance there will be.  In relation to the thickness, I predict that the thicker nichrome wire will produce less resistance.  I assume that as the length of the wire doubles the resistance will also, therefore the current halves, this means I think that resistance is proportional to length and will show a straight line on a graph.

        I predicted that the resistance decreases as the wire increases in thickness.  I will be using a wire that is double the thickness of the previous one, therefore has double the cross-sectional area.

...read more.


To ensure my investigation is fair I plan to ;

image00.png        Keep the voltage as constant as possible, monitoring it at all times and using a variable resistor, which can change the voltage to whichever voltage I plan to use.

image00.png        Disconnect the circuit after every length / thickness of wire to ensure it doesn’t heat up and affect the next reading.

image00.png        Keep the temperature in the room as constant as possible.  This is very difficult


  1. Set up apparatus as shown on diagram 1
  1. Take the readings from the preliminary work to check if there is a suitable          difference between readings, if not, use a wider or smaller range of lengths or thickness or carry on if readings are suitable.  
  1. Connect the first length of wire you plan to use.
  1. Move the variable resistor so that the voltage reading lies on 1.
  1. Take the reading off the ammeter and record it.
  1. As soon as the reading has been taken, disconnect the wire as it may heat up                            

        and this may effect following readings

  1.  Repeat steps 3,4,5 and 6 for the same thickness but a different length.
  1. Once all the results for length have been taken using one thickness of wire, change the thickness and repeat steps 3,4,5 and 6.
  1. Take repeat readings for every thickness and length in order to obtain more accurate readings.

Diagram 1



In the experiment, I was investigating how the length and thickness of a wire affects the resistance.

...read more.


image00.pngTo extend my investigation, it’s possible to explore these factors:

Material – In order to broaden the investigation it’s possible to carry out the experiment as done with the length experiment but by sticking to one length and varying the material.  By doing this it’s possible to compare how each material affects the resistance and conclude which is better for certain appliances.

Temperature – Temperature can have an effect on any experiment calculating resistance as any wire can be heated if connected to a circuit too long.  To investigate how temperature has an effect on resistance, you can heat a certain wire, record the temperature using a thermocouple and then connect it to a circuit and record the resistance.


To do this, I would set up the experiment the same as with the thickness investigation.  In order to investigate how material changes the amount of resistance, I would firstly find different materials e.g copper wire, nichrome wire etc and conduct a preliminary test to see if the different materials had enough difference of values to show the effect of the material on resistance.  If all values of the materials were similar, I would be persistent in finding materials that had significantly different readings.  When I had found suitable materials, I would connect the apparatus the same as Diagram 1, and take readings for each material separately, making sure not to heat the wire as it may cause the wire to effect the final results.

...read more.

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