EMF and Internal Resistance of a cell

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EMF and Internal Resistance of a cell

Data Collection

Data Processing and Presentation

The equation E = V + Ir can be rearranged

E = V + Ir

V = E – Ir

V = –Ir + E

V = (–r) I + E

This allows us to plot V as y against I as x, in order to find the values of E and –r. Because the equation is now in the format y = mx + c, we know that E will be the y-intercept value, and –r will be the gradient.

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I plotted three sets of data for current and voltage: my original results, the values including uncertainties that would give the largest values of E and –r, and the values including uncertainties that would give the smallest values of E and –r.

From the graph, I can calculate both the EMF and the internal resistance of the battery. The y-intercept gives me the value of E, because according to the equation V = (–r) I + E, when the x-value of current (I) is zero, the equation will be simplified to V = E. The gradient of ...

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