This coursework will show how the resistance of a wire, (depending on size of diameter, the thickness and the length) changes. I shall then determine the resistivity of the material (of the wire).

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Planning

This coursework will show how the resistance of a wire, (depending on size of diameter, the thickness and the length) changes. I shall then determine the resistivity of the material (of the wire).

This experiment will be carried out using lab equipment.

Question: How will resistance of a length of wire change with the diameter?

                 How do we determine the resistivity of a material?

Hypothesis-I expect the resistance of a length of wire to increase with a small diameter, and vice verse.  

I expect to find the resistivity of a material by using a formula.

Equipment

  • Variable resistor-this will be used to vary the resistance in the circuit, also trying to keep the voltage constant.
  • Wires-with the least amount of resistance, so they don’t affect the experiment as they can add to the resistance.
  • Voltmeter-to measure the amount of volts going round the circuit, and must have a very high resistance so the electrical current does not go through it (connected in parallel).
  • Ammeter-to measure the current going round the circuit, must have very little resistance so the current may pass through (connected in series).
  • Micrometer-to measure the diameter of the wires very accurately.
  • Crocodile clips-to hold on to the free wires conducting the current through them.
  • Ruler-to measure the length of the wire.
  • Power pack with D.C. current-to supply energy to the circuit and its components.

What will changing my variables do to 1) The resistance of the wire? 2) The resistivity of the wire?

Variables + Constants

  • Changing the wires to test, each having a different diameter.
  • Length-constant at first, but then a variable to test resistance as length changes, at that time diameter will have to be constant.
  • Voltage will have to be a constant using the variable resistor.

The number of measurements or observations that should be made is 2 or 3 depending on time in the lab for the variables + constants. To get the best results I will have to average all my results together. These are key variables as they can be controlled to affect the outcome off the results.

Preliminary Experiment

The whole planning area was based using the results of the preliminary experiment as it showed me what and what not to do.

What did I do?

Well first I used my knowledge from past experiences to setup or organise this preliminary experiment. I then took a set of results down which gave me guide.

What did I learn from it?

I learnt to draw up some conclusions such as, if were to increase the length of the wire I would get results showing resistance increasing also.

My results were as follows:

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What this table should show that as diameter decreases then resistance show increase, this table does not show, that as length of wire increases then so should resistance.

The reason for this is that I only controlled the length of wire, though it does show nichrome has more resistance than constantan.  

Method

I will first gather my apparatus together carefully, and then I shall set them up ready for experimentation. I will connect together the components in an arrangement like this:

Fair test

To make this a fair test I ...

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