(The Usborne Illustrated Dictionary of Science, C. Stockley, C. Oxlade, J. Wertheim, Page 62)
Resistance (R). The ability of an object to resist the flow of current. The value depends on the resistivity of the substance from which the object is made and its shape. The unit of resistance is the ohm (Ω). Electrons moving in the object hit atoms and give them energy, heating the object and using up energy from the source of electromotive force.
(The Usborne Illustrated Dictionary of Science, C. Stockley, C. Oxlade, J. Wertheim, Page 62)
Preliminary Work
From this I can tell I can use 3 volts and resistance wire that is 30SWG.
Prediction
I predict that the longer the wire the more resistance it will have as there are more atoms for the electrons to hit. This will create more heat making the atoms move about more increasing the resistance. Thickness of the wire will have an effect. Thin wire is created by rolling out a thicker peace there is less space between atoms for the electrons to flow through.
Safety
To be safe I will keep the power pack on a low voltage and only leave it on for short periods of time, long enough to get readings. I will also keep the resistance wire on a heat proof mat.
Diagram
Method
- Set up equipment as shown above.
- Measure voltage and current for 100 centimetres of 30 SWG resistance wire.
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Calculate and record resistance using
- Repeat step 2-3 with 90, 80, 70, 60, 50, 40, 30, 20 and 10 centimetres of resistance wire.
- Repeat steps 2-4 another two times.
Results
Graph
Analysis
From the results I can see that my prediction was correct in the fact that I said: I predict that the longer the wire the more resistance it will have. The graph shows that the resistance has positive correlation to the length when kept at a constant temperature. The resistance is proportional to the length. There are some stray results that are probably caused by temperature fluctuations.
Evaluation
To improve this experiment I would use a computer to record the results. I would also use different thicknesses. This would mean I would have to use the resistivity equation:
