In an electrical circuit, a voltage difference:
supplies energy to make charges flow
causes a short circuit
is the term of rate for rate of charge flow
wastes energy

A15,000 kg rocket traveling at +230 m/s turns on its engines. over a 6.0 s period it burns 1,000 kg of fuel. an observer on the ground measures the velocity of the expelled gases to be −1,200 m/s.