Internal Resistance Investigation
I will conduct the following investigation with the aim to find the internal resistance of a lemon battery, which I will construct myself.
The variables that could affect my experiment are as follows:
· Size of lemon - I will conduct my experiment in no longer than an hour, allowing me to use the same lemon for all results
· Size of metal electrodes - I will use the exact same electrodes throughout the whole experiment
· Length of any connecting wires - I will use the exact same wires throughout my experiment and will not break the circuit once I have started collecting data
· Resistance in the circuit - I will vary this using a highly sensitive variable
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The reactions between the electrodes and the solution furnish the circuit with charges continually, this means that the process that produces the electrical energy continues and becomes useful. However, like any battery, this has a limited life. The electrodes undergo chemical reactions that block the flow of electricity. The electromotive force diminishes and the battery will eventually stop working.
Internal resistance: Batteries are not perfect. Use them for a while and you notice they get hot. Where is the heat from? It's from the stored energy in every battery. So batteries turn some of their available energy into heat inside themselves. Therefore, inside the cell you get some energy put IN to the circuit by the cell (an e.m.f.) some energy taken OUT of the circuit by the internal resistor (a pd)
So the pd, V, available to the rest of the circuit is:
V = E - Ir
Where: E = the e.m.f. of the cell
I = the current through the cell
And r = the value of the internal resistance
So Ir = the pd across the internal
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This should make my graph more accurate. At this stage, I cannot see any obvious anomalous results. I noticed straight away as I was doing my experiment that as the volts increased, the amps decreased and this remained consistent throughout. I did not need to make any changes or modifications to my method during the experiment as following my pre-recorded method seemed to work just as I had planned.
Interpretation:
From my results I have used the average of each measurement to construct a graph of voltage against current (see graph) I have drawn a line of best fit and believe from the look of the graph and from the background information I collected earlier that it is a straight line. At first it appears to be a perfect straight line, it then starts to curve slightly. This is because, after a while, all batteries start to deteriorate. The electrodes undergo chemical reactions that begin to block the flow of electricity. The electromotive force diminishes
My aim is to try and find out how much the voltage is affected when
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