And, to continue more ...
In direct current (DC) circuits, the electricity travels in one direction only, from the source through the connections and load and back to the source. In alternating current (AC) circuits, electricity flows in one direction and then quickly reverses to the opposite direction.
Most people understand that electricity is the manifestation of electron movement. It's easy to imagine electrons traveling all the way around the circuit in direct current. However, this visualization tends to fall apart when people consider alternating current. Even at the speed of light, it's difficult to imagine electrons flowing all the way around a circuit and then back again in the opposite direction.
In fact, electrons don't really move much at all. What actually happens is atoms bump into each other and their electrons transfer energy to the electrons on other atoms. This transfer of energy, from electron to electron and atom to atom, is what electricity really is. (Yes, this is a crude description but suitable for our discussion.)
