Experiment 7 - The Internal Resistance of a Battery

A real battery has an internal resistance. It is this internal resistance which help to explain the measurement results from last experiments.

To describe the battery correctly, you introduce a battery, which consists of two parts...

• an ideal battery and
• a Resistor R_i connected in series.

In fact, you are now able to properly explain your measurement results, as you can see from the circuit diagrams shown.

Circuit diagram voltage measurement of a real battery.

Circuit diagram of a real battery with a load resistor.

The internal resistance is not only a theoretical concept. Repeat the experiment 4 and leave the circuit connected for about about 10 minutes. The battery itself heats slightly up. This heat is generated by the internal resistance.

In the next experiments, you examine the consequences of the internal resistance.