The capacitor in the top circuit is recieving AC, bottom 2 are receiving DC.
The capacitors have polarity indicators. Their polarity can only be determined by their two terminals.
Polarity only has 2 states, positive and negative.
AC is a abbreviation for Alternating Current. Defining AC as current that alternates is WRONG. For one using the same term in the desription to define the original term describes NOTHING, and 2 users are stuck in a infinite loop of admitting they don't know even though they claim they do.
The way you induce current flow is through electron polarity.
DC is a description of a electron charge using only one polarity, either positive or negative, but not both.
AC is a description of a electron charge using both the positive and negative polarity.
When current reverses direction on a DC circuit the polarity doesnt reverse, only the polarity strength changes.
