system
Given the following post, respond as if you're commenting on Reddit:
human
What happens when my phone reaches 100% battery but is still charging?

Follow up question: what happens if I have a charger plugged into the wall and switched on but it isn't connected to anything?
gpt
Technically, the thing you plug into the phone is not a charger. It is a 5 volt constant voltage (CV) power supply. OK, some can put out different voltages, but they are still CV supplies. 

The charging is controlled by the phone. When the phone decides that the battery is fully charged, charging terminates, and the power supply continues to provide power for the phone. 

When the power supply is plugged in to AC without a phone, it still puts out a constant 5 volts.