Energy — Know

What is the principle of conservation of energy, and how is it applied to simple energy flow diagrams?

Energy cannot be created or destroyed, only transferred from one store to another or converted from one form to another, so the total energy in a closed system stays constant. In a simple flow diagram, the total width of the arrow(s) entering a process equals the total width of the arrow(s) leaving it, showing that all input energy is accounted for, including any wasted as heat to the surroundings.