Question

Internal Resistance of a battery lab

I'm doing this lab where we have to find the internal resistance of a charged and uncharged battery. We got our data by plotting a V vs I graph, and found the internal resistance of each battery using the slopes of the graphs. From my graphs, I can see that the internal resistance of the charged battery is higher than that of the uncharged one. Which makes sense. However, I'm having a hard time writing the conclusion for this lab. The current increases as the voltage decreases for both batteries, which is obvious, what else am I supposed to say? Any comments I can add?

Answer 1

Discussion and Conclusion

 Source of error ◦ The wire used to connect the circuit contains resistance, so thicker wire should be used to reduce the resistance, so a more accurate result will be obtained.

 Precautions ◦ The multimeter should be set-zero before it is used as an ohmmeter. Set-zero is also necessary when the scale in the ohmmeter is changed. ◦ The resistance box may have poor resistance because of rusting at the contact surfaces. Use sand-paper to polish all the contacting points before use. ◦ Never close the switch while the connection is being made.

 Conclusion ◦ Based on the result of experiment, the internal resistance of the cell was **put your obtained values here** and the e.m.f. E of the cell was **put your given value of emf here** V

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Conclusion:

• The y-intercept of the graph is the EMF.
• The x-intercept of the graph is the maximum electrical current (I).
• The gradient or slope of the graph is the internal resistance (r) = **put your obtained values here**

-------------------------------------you also can add this to conclusion----------------------------------------------------

The common errors of this lab would be the failure to take an instantaneous reading, and an extended circuit connection. To combat the issue of instantaneous readings, we should have either adjusted Logger Pro's Voltage and Current Probe settings to take one, instantaneous reading, or we could have examined our first data point using the "Examine" tool on Logger Pro. We took average readings which probably gave us slightly inaccurate data because of the constant drop in voltage as the chemicals become depleted. This leads us to the next error of extended circuit connection. Due to the overuse of battery-powered objects in day-to-day life, we all know that batteries eventually lose all of their stored energy when out into use. The longer they are powering a circuit, the quicker they will lose their energy. Therefore, the longer our battery was connected to the circuit, the less energy it would have to use the next time it needed to power our light. To be absent of error, a swift touch of the wire to the positive terminal of the **put your given value of emf here** V battery would save energy consumption and give better results because of the minimal energy use, especially with a battery as low as ours. Because we took averages instead of instantaneous readings, we left the circuit connected for longer than we should have, which would make our data less accurate.