Electronics Schematics: The Blueprint of an Electronic Circuit
Electronics schematic diagrams are used to design electronic circuits, just as blueprints are used to design buildings. There are very simple schematics and very complex ones and every complexity in between. Lighting a lamp can be one of the simplest electronics schematic diagrams possible.
This diagram contains two symbols representing the two components in the circuit: a 1.5 V battery and an incandescent lamp. The lines that connect the two components represent conductors, which could be actual wires or traces of copper in a printed circuit board.
In the circuit depicted in this schematic, the positive side of the battery is connected to one lead from the lamp, and the other lead from the lamp is connected to the negative side of the battery. Once these connections are made, current will flow from the battery to the lamp, through the lamp's filament to produce light, and then back to the battery.
Schematic diagrams always depict conventional current flow, which, means that current flows from positive to negative. Thus, the current flows from the positive terminal of the battery through the lamp and then back to the negative terminal of the battery.
In reality, conventional current flow is opposite of the actual flow of electrons through the circuit. The negative side of the battery has an excess of negatively charged particles (extra electrons) whereas the positive side has an excess of positively charged particles (missing electrons). Thus, the electric charge flows through the conductor from the negative side of the battery, through the lamp, and back to the positive side.
As it passes through the lamp, the resistance of the lamp's filament causes the current to heat the filament, which in turn causes the filament to emit visible light.