You know semiconductors as transistors, diodes, and chips. Silicon material is used to make devices that will conduct a certain amount of current when needed.
These devices are made for easy use and with low voltages. You will encounter semiconductor chips in memory devices and computers; transistors are used in many types of circuits, and diodes are used as rectifiers and control devices.
Diodes have an anode and a cathode. The cathode end is marked (+) to indicate which polarity it must be connected to in order to work properly.
Diodes have many uses. They are found in circuits that are used to change ac to dc for certain control devices. They may also be used as protective devices in circuits.
The transistor is used for switching and amplification. It consists of three active elements. There are two basic types of transistors, PNP and NPN.
These terms will be discussed later. E stands for emitter, C stands for collector, and B is used to indicate the base connection.
Switches are used to turn on or off a circuit. They can be made as a simple on off device or used to control many functions in a number of circuits. Switches have names that designate what they can do in terms of turning on or off a circuit or circuits.
For instance, there are SPST (single pole, single throw) switches, DPDT (double pole, double throw), DPST (double pole, single throw), single-pole, six-position, and so forth.
Relays are switches that are moved electrically instead of by hand. They can be made in almost any configuration of poles, throws, and construction.
The force that operates a relay is magnetic. The magnetic pull is produced by current passing through a coil of wire. The attraction of an armature causes the switch sections to operate