Internal Resistance and Terminal Potential Difference
Key points
- Real batteries have internal resistance, represented by the variable, r.
- This internal resistance reduces the voltage from the ideal potential difference (emf).
Batteries have resistance to them. This means that the ideal potential difference provided by the EMF is not the same as the actual voltage output.
- Internal resistance is inside, and connected in series to the battery.
- For a real battery, the EMF is only equal to the voltage output if no current passes through it.
- As current passes through, the internal resistance decreases the voltage.
- The equation to the right shows how to find the voltage given the EMF, current, and internal resistance.
- Potential difference drop is determined by multiplying the current passing through the battery by its internal resistance. (from V=IR).
Formula Booklet
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