Assess the effect length on the resistance of brine soaked paper

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Physics Coursework


In this project, I am trying to assess the effect length on the resistance of brine soaked paper.

To do this, I am attempting to measure the current flowing through a circuit with the paper in.

In order to start the experiment, I will need the following apparatus:-

Here is a circuit diagram of the proposed experiment:

Here is a diagram of how the retort stand will be arranged:


Before starting my main experiment, I performed a preliminary experiment that helped me to determine what unforeseen obstacles or difficulties I would encounter:

  1. I found that the paper becomes too fragile to handle when it is over 30cm long. It breaks when soaked in water.
  2. I found that water stays evenly soaked onto the paper when it is clamped in a horizontal position
  3. I found that the saline solution causes salty deposits to be left on the Bull-dog clips.
  4. I found that high voltages are detrimental to the experiment as they decrease the readings to quickly due to electrolysis. The experiment has to be carried out quickly and efficiently or the too much of the brine will ionise.
  5. I found that rust occurs on the bull-dog clips that has to be sanded off between tests, to keep the readings accurate and the electrode clean. – An extra material I will need is sand-paper.

To keep the experiment safe, no liquids will be allowed near any power points and any obvious hazards will be removed.

This was a useful trial that helped me establish and resolve any difficulties.


I am going to attempt to calculate the effects of length on the resistance of brine soaked paper by first setting up my equipment as shown. Paper of the desired length is saturated with brine solution and then attached to the circuit using the bull-dog clips. Voltages starting at 5, and increasing by intervals of 1 volt up to 8 volts are passed across the paper and the resultant amperage readings recorded. I am using these voltages as if I used much higher voltages, electrolysis would occur faster and therefore current would decrease faster, reducing the accuracy of my results.

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Paper will be cut in the following lengths to be tested:

5cm, 10cm, 15cm, 20cm, 25cm, 30cm.

It will be a fair test as I am using a constant voltage, keeping the paper horizontal so the solution is spread evenly, and also cleaning the bull-dog clips with glass paper before each set of results. As well as this, both the width and the thickness of the paper will remain constant.

I am taking readings from 4 voltage sets so as to get an average and make the results fair.


During the experiment, ...

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