Electronics · DC circuits / Principles and inquiry
Battery internal resistance experiment guide
Vary the load to measure terminal voltage and current and determine internal resistance.
How does it work?
The slope of V versus I is −r; the intercept is the EMF.
Key relationship
I = E/(R+r) · V = E−Ir · P = I²R
Try this investigation
- Vary the load to measure terminal voltage and current and determine internal resistance.
- Run and record each of the three baseline presets.
- Compare the changed variable and its result with the baseline records.
Interpreting your results
What is the internal resistance if this battery's V–I slope is −1 V/A?
1 Ω
Assumptions and limitations
EMF and internal resistance are constant. Chemical reactions and battery life are omitted. Experiment on screen; do not reproduce this with real power supplies, outlets or high voltage.