When you are using a laptop with Ubuntu, you will probably see a battery icon near the clock, or a power plug icon if you have it plugged in:

You may not want the power plug icon to show up when you have the computer plugged in, or you may have a misconfigured installation where it always shows up. Either way, it’s a simple change.

Navigate to System \ Preferences \ Power Management

Here you can set when the battery/power icon will be displayed.