All forms of electronic devices consist of a variety components. Some of these are passive (they obey simple laws), and some are active

Passive Components


Resistor is a two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

Resistance is expressed in Ohms, and the amount of resistance can be from zero ohms up to millions of ohms. The amount of resistance is indicated by a colour code painted on each device. It's important to note that all wires (and cables) have resistance but its normally measured in fractions of one ohm per meter.




Capacitor In its simplest form a capacitor is two plates very close together but never touching. It is two-terminal electronic component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. Some capacitors have a dielectric between the plates to enhance the capacity.

Even though they store electric charge the amount is too small to be used as a replacement battery, but can be used as for timing, passing AC only and smoothing the voltage inside electronic devices.





Coil (Inductor) as it's name suggests is a coil of wire, normally made from copper and sometimes is wound around a ferrite core to increase it's effect. It is a passive electronic component that stores energy in the form of a magnetic field. Coils can be used in many ways.



Active Components

diode Allows electricity to go in one direction but not the other.

Transistor Can control a large current flow with a much smaller one, this can be used for amplification.

Thermionic Valve is similar to a transistor but much less efficient and reliable.

More to follow ...