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I am going to investigate the factors that affect how well graphite coated paper conducts electricity. Graphite Paper is paper coated with graphite on one side; it is a semi-conductor.

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Introduction

I am going to investigate the factors that affect how well graphite coated paper conducts electricity.

Graphite Paper is paper coated with graphite on one side; it is a semi-conductor.

I will be investigating how the width of the graphite paper affects the current and the resistance. I will also be investigating how the temperature of the graphite paper affects the resistance.

The resistance of a conductor is defined by: -

                                      R =

V is p.d across paper

        I is current through paper

A current only flows between two points if the electrical potentials at the two points are different. The higher the potential difference at one point, the faster the current will flow between them. If the two points have equal electrical potentials, no current will flow between them.

Just imagine the wire to be a plank of wood; and the current to be a ball. If there is no potential difference between the two ends of the plank, the ball will not roll to either side.

image00.png

 If the potential of one side of the plank is made bigger, the ball will roll towards the other side.

image01.png

The more the potential on one side is increased, the faster the ball will roll to the other side.

image02.png

...read more.

Middle

image03.png

I predict that when I increase the temperature, the resistance will go down. I believe this to be the case because on page 245 of Physics by Hutchings it says that carbon has a negative temperature coefficient of resistance. Graphite is a form of carbon, and should behave in the same way.

Below is what I expect my graph to look like.

image04.png

Method 1 (width of paper)

Apparatus.

7 wires.

Ammeter

Voltmeter

Variable resister

2 Cells

2 pieces of Graphite paper

Scissors

2 Modified bull dog clips

Circuit Diagram.

image05.png

  1. Measure the width of the graphite paper, and draw 7 lines of equal distance from each other along the length of the paper.
  2. Set up the circuit (see diagram above)
  3. Place the graphite paper in the bulldog clips.
  4. Alter the variable resister to make the p.d 1 volt.
  5. Take the graphite paper out of the clips and cut with scissors down the next line.
  6. Repeat stages 3-5, until you have 7 readings.
  7. Divide the voltage by the current to give resistance.
  8. Repeat the whole experiment with two cells, but altering the variable resister to make the p.d two volts.

I will use an analogue ammeter as it gives a more accurate reading.  

Method 2 (temperature of paper)

Apparatus

Wires

Emersion heater

Large beaker

Graphite paper

Water

Thermometer

Ohmmeter

2 Modified bull dog clips

Circuit Diagram

image06.png

...read more.

Conclusion

I could also use a narrower range of values for the width of the paper; maybe go down in 0.5cm instead of 1cm.  

Nevertheless, my graphs allowed me to draw a decent conclusion from the experiment (see analysis) and see a pattern, and see quantitatively what the pattern did.

Evaluation 1 (temperature of paper)

I again think that my experiment worked well because my results were consistent with each other. I received no anomalous results, which again must mean that my experiment was a success. However my results were not perfect as the points did not all lie on the same line. This could be because of the condensation, which would have slightly dampened the paper, altering how much current can pass through it. To improve the experiment you could wrap the paper around a light bulb to heat it, and use a variable resister to change the temperature. But it would be difficult to measure the temperature of the paper.

Nevertheless, my graph allowed me to draw a decent conclusion from the experiment (see analysis) and see a pattern, but I could not see quantitatively see what this pattern did.

...read more.

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