An Investigation Into the Resistance of a Wire - GCSE Physics Coursework

Updated on December 30, 2016


In this article I will investigate what affects the resistance of a wire.

Electricity flows in metals. Metal wires are made of millions of tiny metal crystals, and each crystal’s atoms are arranged in a regular pattern. The metal is full of "free" electrons that do not stick to any particular atom; rather, they fill the space between the atoms. When these electrons move, they create an electric current.

Conductors have resistance, but some are worse than others. The free electrons keep bumping into atoms. A wire's resistance depends on four main factors:

  • Resistivity
  • Length of the wire
  • Cross-sectional area
  • Temperature of the wire

I will investigate how the length of the wire affects the resistance. I have done a preliminary experiment to help me decide the best way to do my investigation. The results will help me make predictions, as well.

Preliminary Investigation

Below are my results from the preliminary experiment (see Table 1). To ensure accuracy, I have taken three readings each of volts and current.

Table 1: Preliminary Results

These results show that as the length of the wire increases, the resistance increases, as well. Furthermore, if you double the length of the wire, the resistance is roughly doubled. For example, when the length of the wire is 20cm the resistance is 3.14 ohms; when the length of the wire is 40cm the resistance is 6.18 ohms, which is roughly double. In my main investigation I will see if this observation applies to my results.

I found that the apparatus I used was suitable, but I think that I could possibly increase the number of data points to generate more reliable results, perhaps by increasing the length of the wire by 5cm each time, instead of by 10cm.

Investigating the Resistance of a Wire


I will investigate the resistance of a wire in relation to its length.


I predict that the longer the wire, the larger the resistance. This is because the free electrons in the wire bump into more atoms, thereby making it harder for electricity to flow. Similarly, the shorter the wire, the smaller the resistance because there will be fewer atoms for the electrons to bump into, thereby easing the flow of electricity. Furthermore, the resistance of a wire is directly proportional to the length and inversely proportional to the area, so doubling the length of a wire should increase the resistance by a factor of two. This is because if the length of the wire is doubled, the electrons bump into twice as many atoms, so there will be twice as much resistance. If this is correct, the graph should show a positive correlation.


The apparatus I will use in this experiment is as follows:

  • 1 ammeter (to measure current)
  • 1 voltmeter (to measure voltage)
  • 5 x wires
  • 2 crocodile clips
  • Power pack
  • 100cm nichrome wire


First, I will collect the apparatus I need and set it up as shown in Diagram 1, below. Next, I will set the power pack on the lowest voltage possible to ensure that the current passing through the circuit isn't too high (which could potentially affect the results because the wire would get too hot).

I will place one crocodile clip at 0cm on the wire and the other at 5cm to complete the circuit. I will then turn the power pack on and record what voltmeter and ammeter readings. I will switch off the power pack, move the crocodile clip that was at 5cm up to 10cm, and switch on the power pack. Again, I will record the voltmeter and ammeter readings and turn off the power pack. I will repeat this method every 5cm until I get up to 100cm, taking three readings from both the voltmeter and ammeter each time to ensure accuracy. In addition, after each reading I will switch the power pack off to ensure that the wire doesn’t get too hot and affect my results.

Diagram 1: Apparatus

Ensuring Accuracy

To ensure accuracy I will record the voltage and the current three times every 5cm and take the average reading. This will reduce the chance of false readings and will cancel out any anomalous results. I will also ensure that the wire does not heat up too much by confirming that I do not set the voltage too high on the power pack and by maintaining the same the voltage for every reading. In addition, I will make sure I turn the power pack off after each reading. I will try to make this investigation as accurate as possible.


There are different variables that can be changed in this experiment; these are the independent variable. However, due to my line of enquiry, I will only change the length of the wire. The variables I will control will be the type of wire (resistivity) and the cross-sectional area of the wire. I will also control, using the power pack, how many volts pass through the wire. Below is a table illustrating the effect of changing the variables (see Table 2):

Table 2: Variables


I will ensure experimental safety by confirming that all the wires are connected properly and that none of the insulation on the wires is worn. I will also ensure that there is a clear indication that the power is isolated by means of a switch and an L.E.D. I will stand up during the investigation to ensure that I do not injure myself if something breaks.


Below is a table of my results (Table 3). I have taken three reading and have worked out the average, shown in red.

Table 3: Results

Table 4: Length & Resistance

Table 3 shows that as the length of the wire increases, the resistance increases, as well. This confirms the first part of my prediction: that the longer the wire the larger the resistance.

In addition, my prediction that doubling the length of the wire increases the resistance by a factor of two is correct (see Table 4).


Graphing these results shows a nearly straight line, illustrating a strong positive correlation between length and resistance, which is consistent with my prediction.


Overall, my results are very consistent with my predictions. Most of the data points were on, or very close to, the line of best fit. There are a few data points that are farther away from the line of best fit than the others, but they are still consistent with the general trend. There are no anomalous results that I would consider to be far away from the line of best fit.

There are possible sources of error that might have led to inconsistent results, such as a kink in the wire. This would have prevented the area of the wire from remaining constant and would have affected my results. However, I made sure that the wire remained straight throughout the experiment.

I think that the range of my results was sufficient enough for me to draw a valid conclusion about how the length of the wire affected the resistance. This was because I could plot a graph and show the general trend.

I think that the pattern/general trend would continue beyond the range of values I used. However, I think that unless I had specialist equipment the results would be distorted because the wire would eventually get very hot. Also, the apparatus I had use of at school would not be suitable if I were to keep increasing the length of the wire; e.g., in a classroom environment I could not increase the length to more than 150cm because of safety concerns as well as space constraints.

I think my method could have been improved to produce results that were even more consistent. I could have considered using a new piece of wire each time in order to regulate the temperature more stringently. Using the same piece of wire throughout the experiment meant its temperature rose slightly over time, which may have affected my results. However, using new pieces of wire each time would have been too impractical and time-consuming in the context of this lesson. Overall, I think my method was sufficient to obtain reliable results.

To support my prediction and conclusion, I could do further experiments. For example, I could use different types of wire instead of using only nichrome. I could also consider using different cross-sectional areas of wires or even change the temperature of the wires deliberately and see how manipulating these variables affect the resistance of the wire.


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    • profile image

      Chicken Muncher 4 weeks ago

      You are incorrect about the doubling the length of wire = the resistance increases by a factor of two.

      I used some of the data for my physics homework so thanks for that.

      Just remember to keep on munching chicken like me

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      ali 2 months ago

      i copied and pasted the whole thing for my hw and it was very good thank you

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      charlie houghton 3 months ago

      thank you so much this really helped me understand this experiment!

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      rio 4 months ago

      had the perfect answers but for the conclusion you needed to add an example of your results, that's what my science teacher says, besides that , this is a great source of information really helped me with my homework

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      kcds 4 months ago

      you just finished my assignment :D thanks man

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      bob 11 months ago

      Good work. Well done, Gold Star. :)

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      angel kyeremeh 11 months ago

      this is so beautiful. well done!

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      Teresa June 12 months ago

      What was the SWG (Standard Wire Gauge) or diameter of your wire? I know you stated it was Nichrome, and 100 cm long, but the SWG is not stated - Am using your data as secondary data and need to compare my investigation and yours.

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      sb? 12 months ago

      you just completed an assignment for me thank boi

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      Retep882 12 months ago

      This is by far the beast source of information I could find for my coursework, you are awesome:)

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      Miss forgetful. 13 months ago

      Thank you so much for this as it helped a lot in my physics class.

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      Elliott Hobnob 13 months ago

      hi its elliot here

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      Callum Twizell 13 months ago

      I have Ibra Messi and Saurez in my concept squad!

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      misha 14 months ago

      i'm back

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      Hello 14 months ago

      What are the references you used?

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      yaas 14 months ago


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      mr stone 15 months ago

      really helpful for my physics contorlled assessment

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      The funny thing is i'm not a girl :/

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      I got side tracked with all the adverts

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      Bish Bash Bosh k 15 months ago


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      Anonymous 15 months ago

      What is the diameter or the SWG of the wire used?

    • profile image

      CAL 18 months ago


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      gracealbam 18 months ago

      Omg thanks so much

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      Lono13 18 months ago

      Love this lono 2012, what a geeza

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      doritoman 19 months ago

      This was really helpful for my controlled assessment. luv u

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      mehitsme 21 months ago

      do you know what the thickness of the wire is? it doesnt say on here and it would be really good information for those like me who need to use it as a secondary source in their controlled assessments.

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      Ben 2 years ago

      Thanks, I needed a secondary data source for my controlled assessment.

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      Dayanara 3 years ago

      I'm quite pleased with the inootmarifn in this one. TY!

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      Luno2012 4 years ago from United Kingdom

      @ehehfeelgood - the coursework is for GCSE students and those in secondary School.

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      ehehfeelgood 4 years ago

      Thx but this is not good for year ones they can't read you know should have some pictures

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      Darius 4 years ago

      Thanks! This had really helped me with my Year 9 work. I really appreciate the info you have logged into this. Once again, thank you!

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      omt8 4 years ago

      Great help. Helped my year 9 coursework a lot. thanks

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      Luno2012 4 years ago from United Kingdom

      Sam: No worries.

      MrsBonnersSciencePupil: Glad I could help!

      Lucy: Glad to hear it, Lucy. Best of luck with your future tests and exams.

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      Lucy 4 years ago

      hi this was really helpful im currently doing my CAU for year 11 and this was a great help thanks

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      MrsBonnersSciencePupil 4 years ago

      This was really helpful for my controlled assessment. luv u

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      sam waiganjo kenya 5 years ago

      thnx a lot

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      Resolver2009 5 years ago from Bournemouth, UK / Oslo, Norway

      Voted up :) Must be of great help for those students who are doing physics.