Schematic diagrams use symbols to show how electrical components are connected in a circuit. Schematic diagrams provide no indication of the physical size or location of any of the components, only they're functioned and how they are related together electrically. Here is a pictorial diagram of our familiar flashlight. Here's how the schematic of the simple flashlight circuit could be drawn. Here's the schematic diagram on the right is much simpler and therefore easier to follow than the pictorial diagram on the left. In fact, this is why we use schematic diagrams when we are only interested in the electrical characteristics of the components and how they are interconnected. It is important to take time to make sure we understand the correspondence between the components in the flashlight diagram on the left and how each is represented in the schematic diagram on the right, including the conductors that make up the electrical connections. First, consider the components beginning with the power source, which in this case is a single cell battery. In the pictorial diagram on the left, the battery is drawn so that it can be recognized as a battery, but on the schematic diagram on the right, it is drawn more compactly by using this symbol for a battery. Next, the control device, in this case a push button switch, is drawn in the schematic using the generic symbol for a switch. The switch has been drawn with its contacts closed. This is the position that allows current to flow through the components and conductors that make up the circuit. The last electrical component in this circuit is the load, in this case a lamp. Again, the schematic symbol for the lamp is much simpler than a pictorial drawing. Now we will define the direction of current flow in an electric circuit. First, recall that current is defined as the movement of charged particles. Electrons are charged particles, so when electrons move in a circuit, this constitutes current flow. On a schematic diagram, a DC current through a wire or a component is labeled with an uppercase I, along with an arrow to indicate the direction of current flow. The energy source establishes an electromotive force or voltage in the circuit, and it is this force that causes the electrons to move. More specifically, electrons have a negative charge so that they are at the same time repelled away from the negative terminal and attracted towards the positive terminal of the battery. If there is conductive path through which the electrons can move under the influence of this force, they travel through the wires, through the closed switch, through the load, and return to the positive terminal of the battery. In this course, we will use the electron current flow, as shown here. By convention, physicists and engineers generally consider current to flow in the opposite direction, which is called conventional current flow.