Diagram showing the direction of current flow through an electric power source such as a battery or electric generator, or other active component (on the left), and through an electrical load such as a resistor, light bulb, electric motor, or other passive electrical device (on the right).

In a power source the electric current i flows into the negative terminal and out of the positive terminal. So the positive electric charges are forced to move in the opposite direction to the electric field E, i.e. in the direction of increasing electric potential gradient. Hence, work must be done on the charges to make them move in this direction, so the potential energy of the charges (color) is increased, and electric power p < 0 flows out of the active component, which must have some kind of a source of power on its own (yellow arrows on its left), into the electric circuit located on the source's right.

In contrast, in an electrical load such as a resistor, light bulb, electric motor, or other passive component (on the right), the current flows into the positive terminal and out of the negative terminal, hence the positive charges move under the influence of the electric field E in the direction of lower electric potential (voltage). Doing so, charges perform work on the component, losing their potential energy (color), and electric power p > 0 flows out of the electric circuit located at the load's left first into the load itself, and furthermore its surrounding (yellow arrows on its right).