internal resistance of a battery planning
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Introduction
Physics coursework
Investigation to compare the internal resistance’s of different cells.
My task is to compare the internal resistances of different cells. I will first make a prediction what I think the relation may be. Then I will carry out preliminary and final experiments. After this I will then evaluate and analyse all of my results.
Internal resistance is:
“The resistance within a voltage source, such as an electric cell or generator.” (http://www.answers.com/topic/internal-resistance-electricity)
EMF (electromotive force)
“The energy per unit charge that is converted reversibly from chemical, mechanical, or other forms of energy into electrical energy in a battery or dynamo.” (http://www.answers.com/topic/electromotive-force)
No real devices (batteries, amplifiers, generators) are perfect and so all have an internal resistance. The resistance is caused because the charge has to flow through the cell. When it does
Middle
I set up the experiment as below. Then I put different cell in and changed the resistance on the rheostat and recorded the results.
Conclusion
9
3.27
2.01
9
2.46
0.77
1.5
1.6
0.13
1.5
1.59
0.17
1.5
1.58
0.2
1.5
1.57
0.22
1.5
1.56
0.25
1.5
1.54
0.29
1.5
1.5
0.39
1.5
1.47
0.47
1.5
1.43
0.58
1.5
1.38
0.69
1.5
1.07
1.75
1.5
0.46
3.75
When doing my preliminary experiment I discovered that it would be better to use digital voltmeters and ammeters rather than one I used as it would be more accurate to use a digital ammeter and voltmeter. This ensures there will be no errors when reading the values. In my real experiment will also take repeats and also I will use more cells.
The Real Experiment Method
I will set up the experiment as below. I will implement different cells and change the resistance to get at least 8 readings for each cell. I will wait for the equipment to cool down between each reading. I will also use the same equipment throughout to attempt to stop any anomalies occurring.
Safety
The experiment is very safe and so all I need to do is ensure the batteries do not get hot and that they do not leak as the contain very harmful and corrosive chemicals.
This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.
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