A "closed" circuit is just an open circuit plus a pump (electron pump or water pump). Open circuits work fine if there is a powerful source of electricity (lik

A "closed" circuit is just an open circuit plus a pump (electron pump or water pump). Open circuits work fine if there is a powerful source of electricity (like a a radio) and a sink (like the Earth), and same for water (an icy comet crashing into a cliff, making a waterfall). An open water circuit is full of stationary water.