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 the line of best fit gives me the negative value of internal resistance (r), because the gradient can be calculated by y/ x, which is represented as V/ I in our results.
Conclusion
From my results, I found that voltage and current had a negative correlation, as as one increases, the other decreases.
The values I obtained are EMF = 2.402V and r = 3.814Ω.
The literature value for EMF was 2.35V, because when I was recording results, I obtained this value for voltage when current equaled zero. The literature value and the experimental value have a relatively small difference, which indicates that the experiment could be considered successful to some extent.
Evaluation
The investigation showed no anomalous results in general, as increasing values of voltage all resulted in decreasing values of current. This is consistent with previous knowledge learned.
The same pieces of equipment were used throughout the entire experiment, as changing these would have affected the results from the battery. There were limitations as to the accuracy of the readings that I could obtain using said equipment; to reduce the possible error range of the final result, I could replace the current pieces of equipment with more accurate ones.
The variable resistor was not given time to cool down in between our recordings, so the temperature might’ve affected the results in some way. I only obtained five results, which might not have been enough for the experiment to really be considered accurate. Next time, I will record more paired values of the current and the voltage, as well as repeat the experiment at least once to reduce the chance of inaccuracy.