Resistance of a wire.

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Science Coursework

Title:Resistance of a wire

Aim: To investigate the affects of length in the resistance of wire.

Apparatus: Voltmeter

Ammeter

Connecting wires

Batteries

Straight wires

Batteries

Straight wire

Ruler

Clips

Constantan Wires - SWG value of 26

Switch/Variable Resistor

Procedure: There are different factors that affect resistance from the below we will see which one is the best to experiment with. The material affects the resistance due to the fact that some metals are better conductors than others. For example, copper is better than nichrome as a conductor due to a bigger amount of electrons. However, using this to test resistance would be difficult due to insufficient equipment in the laboratories. I would have to get a variety of metals, which we don't have.

The temperature affects resistance because when it heats up the atoms in the wire start to vibrate. This increases the amount of collisions between atoms and electrons. The collisions means loss of energy and this increases the resistance. This would be hard to test because with the insufficient equipment we have, it would be difficult to test it accurately. We could test the resistance of the wire width because if there is more space there will be fewer collisions due to more space for the electrons to flow. This would decrease the resistance. This would be a good experiment, but would be quite challenging. Finally we could test the length of the wire also because the longer the distance, the further the electrons will travel, therefore this means the length should decrease/increase directly proportional to the resistance. Wire length is a simple experiment to obtain results and we have all the equipment to carry out the experiment.

To keep it a fair test I can only change one thing, the length. Therefore I have to keep all other factors that will affect resistance the same. This means we have to use the same material, use a wire with the same cross - sectional area and keep the temperature the same. This is going to be difficult as the wire increases in temperature when switched on. Therefore, to keep it a fair test, we have to immediately disconnect the circuit as soon as we have got the reading so it doesn't heat up.
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To keep this experiment safe we will be careful while touching the wires in case they are hot. We will not use a high voltage, so the wire will not burn and we will start with the lowest current, so it won't melt immediately.

Method: 1.Set up equipment like diagram

2.Press down switch

3.Start at 10cm of the wire length

4.Take reading of current and voltage and note it down in the table

5.Take finger of switch

6.Move wire to 20cm and repeat

7.Repeat ...

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