Yes, that is a basic misunderstanding. The Arduino board is designed to still work with both external voltage applied and plugged into USB port. The auto-voltage sensor circuit on the board will default to use external power if it's available.
Lefty
Yes, that is a basic misunderstanding. The Arduino board is designed to still work with both external voltage applied and plugged into USB port. The auto-voltage sensor circuit on the board will default to use external power if it's available.
Lefty