• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To investigate the resistance of a conducting material as its length changes.

Extracts from this document...

Introduction

Christopher de Wardt                                                         Dulwich College

Physics Coursework 2002

Planning

Introduction

Aim: To investigate the resistance of a conducting material as its length changes.

        I am carrying out this experiment to find out if as a result of changing the length of a conducting material – graphite paper in my case, the resistance changes directly because of this change. In order to make sure that the results, leading to further conclusions, are reliable, I must make sure that any other factors that could possibly affect resistance are kept constant.

Variable Studied - Length

        I will be using a circuit method in this investigation; there are a number of different factors that I must take into account when investigating the resistance of the graphite paper. Obviously, the first is length, which I will decrease from its starting length in equal steps as it approaches zero centimetres long; this is the main variable being considered in my investigation. The width of the paper must also be kept constant, as it may affect the results, and causing the investigation to become unfair.  To evaluate the resistance of the graphite paper I will record my observations in terms of voltage across the paper and the current of the circuit. Because

...read more.

Middle

20

3.35

30

3.29

40

3.24

50

3.19

60

3.14

70

3.09

80

3.05

image10.png

Conclusion of preliminary experiment:

As the maximum temperature change of the lab environment is only likely to be around a few degrees at the very most, my results suggest that the decrease of accuracy of my main experiment will be very small. For example, my graph shows that if there was a change of temperature from 20ºC to 22ºC in the lab, the accuracy of my results would 0.012kΩ too high, which would be a percentage error of around +0.36%. Therefore, in the context of this experiment, temperature will have almost no effect on the reliability of my results in the lab environment.

Method of main experiment

Apparatus:

                • 2 Volt cyclon cell

                • Analogue ammeter

                • Digital voltmeter

                • 45 cm strip of graphite-coated paper

                • Rheostat (potential divider)

                • Circuit wires

                • Modified Bulldog clips (2)

image06.png

The circuit should be assembled as shown above; the slide on the rheostat should always be adjusted so that the digital voltmeter reads 1 volt.

The current should be recorded for the following lengths of graphite paper:

Voltage/V

Length/cm

1

45

1

40

1

35

1

30

1

25

1

20

1

15

1

10

1

5

As shown in the table, and as I wrote earlier, voltage must be kept constant to make this a fair experiment. Also, the width of the graphite paper must be kept constant throughout the experiment – easily done by simply using the same piece of graphite paper cut to shorter and shorter lengths.

...read more.

Conclusion

-1 and as voltage was kept constant at 1 Volt in this experiment, effectively R=I-1. Because of this, and the line of best fit seems to suggest a ‘squared’ relationship, I believe a graph showing resistance against length would show a direct proportionality.

image12.png

        This graph shows that Resistance increases with length; it shows that resistance is directly proportional to length. Specifically for my width of graphite paper it shows that R= ~70*length. The fact that resistance has been shown to be directly proportional to length - in this case - fully supports my prediction.

This allows me to conclude that the scientific basis for my prediction was sound, and that the number of collisions between electrons and atom sites determines the value of resistance in a conductor.

Evaluation

        As I found that my results fell in line with previous scientific knowledge, it suggests that my experiment was carried out accurately, and that the use of repeat readings is a good way of getting closer to the ‘ideal’ values which previous scientific study suggests I should be finding. The accuracy of my results also shows that my conclusions have a firm basis; by comparing my own personal results with others carrying out similar experiments, they seem to be similar enough to ensure that they are accurate. In order to make sure these results are reliable, even further amounts of readings could be taken using different sets of equipment to ensure that the experiment remains fair.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Marked by a teacher

    Determining Avogadro's Number Lab

    4 star(s)

    Thus, the time after 10 minutes is 600 seconds �0.833%. Charge: After 10 minutes Average charge = average current x time Average charge = 0.9 A x 600 seconds Average charge = 540 C Percent uncertainty

  2. Thermistor Coursework

    I think that this could be the source of any anomalous results, such as the results for 10°C and 25°C. Another reason for there being anomalous results is that the sensor unit didn't have enough time to stabilise before I took my reading.

  1. Investigating the effect of 'length' on the resistance of a wire

    * Two screws. * Two nails. * A micrometer. * A calculator to calculate the resistance and the mean average for each length. Diagram: Planned Method: The ruler will be put in the centre of the wooden plank and it would be nailed into it by two nails. After the ruler has been anchored on the plank of wood,

  2. I am going to investigate what the resistivity is of a pencil lead. ...

    I will place the crocodile clips on the end of the pencil lead and take the width of the clips off the total length of the lead. The reason I will do this is because the crocodile clips will be conducting the electricity at the points where they are attached so the lead is only conducting past these clips.

  1. The aim of the experiment is to verify the maximum power theorem and investigate ...

    The scale of the spring balance is not firmly attached to the balance. When we pull the spring balance and hence the blocks, there must be vibration of the balance. The scale then is not set to zero. The reading we taken will be inaccurate and then inaccurate calculated values

  2. My aim is to investigate at which temperatures will give me which resistance and ...

    43.7 100 29 35 34 32.7 The anomalies would of caused the results to come out wrong. These results could of happened due to a number of reasons. One is if the thermistor was not in thermal equilibrium, this means that the thermistor may not of been at the same temperature as the water it was placed in.

  1. physics sensor coursework

    However, the graph does not show linearity, which means that a change in either variable will not lead to the same proportional change in the other. The relationship can be explained in terms of the amount of charge carriers in the LDR.

  2. Physics Coursework - Factors that affect the resistance of brine-soaked paper

    Diagram: RESULTS Length of paper (cm) Voltage (V) Current (mA) Resistance (k) 1 5 5.21 1.61 3.236 6 5.02 1.48 3.391 7 5.01 1.20 4.175 8 5.00 1.16 4.237 9 5.02 1.07 4.691 10 5.02 0.94 5.340 2 5 5.02 1.72 2.918 6 5.00 1.60 3.125 7 5.01 1.23 4.073 8 5.02 1.26 3.984 9 5.02 1.08 4.648

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work