Enter the electromotive force, current, and load resistance into the calculator to determine the internal resistance.

## Internal Resistance Formula

The following formula is used to calculate an internal resistance.

r = (e / i) – R

- Where r is the internal resistance (ohms)
- e is the electromotive force (Volts)
- i is the current (amps)
- R is the resistance of the load in the circuit.

## FAQ

**What is an internal resistance?**

An internal resistance is the resistance to the flow of electricity due to the internal structure of a circuit or system.

## Example

How to calculate the internal resistance?

**First, determine the electromotive force.**For this example we will say this value is 10 V.

**Next, determine the current.**For this example we will assume a current of 10 amps.

**Next, determine the load resistance.**For this example the value is 20 ohms.

**Finally, calculate the internal resistance.**Using the formula we find the internal resistance to be : 10/10 – 20 = -19 ohms.

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