Experiment 3 - The Charging Current

When loading a capacitor, a current flows. Once the capacitor is fully charged, the current dries up. Can you observe this behaviour and the current? To do so, repeat "Experiment 1".

Consider the circuit shown. You recognize the circuit from "Experiment 1". Only this time you have replaced the ceramic capacitor by an electrolytic capacitor with a capacity of more than a thousand times larger.

Circuit with electrolytic capacitor. (Enlarge)

Circuit diagram with electrolytic capacitor.

The flow of electrons during charging is called charging current. With the LED you are watching it. Build the circuit shown. While setting up the circuit pay attention to the polarity of the electrolytic capacitor.

• If you press the pushbutton switch , the LED lights up briefly due to the charging current.
• If you press the push button again, the LED remains dark. The capacitor is already charged and therefore no charging current flows.

In the next experiment, you complete the circuit in order to be able to discharge the capacitor again.