Experiment 4 - The Load Circuit

A battery not only provides a voltage. If a light bulb, electric motor or heating element is included in the circuit, a current flows. This lights up the bulb, the motor turns and the resistance heats up.

Build the circuit shown. You connect to a load resistor to the battery. As a result, a current flows through the resistor and the resistor heats up.

Circuit with Load Resistor. (Enlarge)

Circuit diagram with load resistor.

Warning In the experiments the load resistor gets very hot... Do not touch the resistor during the experiments! To avoid damage to the breadboard keep some distance between the resistor and the breadboard (see picture).

Setup of load resistor on the breadboard. (Enlarge)

With a multimeter you measure the current. By Ohm's law you can calculate the current that flows through the resistor...

I = U / R = 9 Volt / 10 Ω = 0.9 A

You can surely confirm, that the measured current is less than the current you would expect according to Ohm's law. You measure a current of 0.8 A.

Why is that? This becomes clear in the following experiments.