Switches are now constructed of thermosetting plastic, which is becoming increasingly common. It's no surprise that the materials utilized for switches, such as porcelain, bakelite, and thermosetting plastic, must be poor conductors of electricity. Leo Baekeland, a Belgian scientist, invented thermoset plastic in 1906. He called his invention "the material of destiny." Today, this same material is used to make switches, buttons, and other mechanical components.
Before plastics were available, people made switches out of metal. The first mass-manufactured switch may have been an Edison button manufactured around 1882. By the 1930s, most homes had their own light switch located near the door. In more modern homes, the switch is often located near the wall socket.
Today, switches are usually made from silicone or rubber. These materials are nonconductive and can't transmit electricity, so they don't burn when you touch them. They also feel nice when you touch them. A small amount of dust or dirt won't affect their performance.
The contacts inside the switch box are made from copper or aluminum. When you turn a knob or slide a piece of furniture, you're touching these metals together. A spark might happen if you have an oil-soaked hand or if there's any moisture in the atmosphere. But overall, switches are very safe devices; only real prosals need to worry about electric shocks from switches.
Earlier switches were surface-mounted porcelain and worked as rotary switches with a rotational mechanism. Later, more durable materials such as Bakelite and ebonite were utilized. They are now constructed of contemporary polymers such as polycarbonate or fire-resistant ABS. The actual switch component is usually made of steel or aluminum.
Switches can be found inside almost every home built after 1950. Switched outlets for modular furniture such as bookcases and desks became popular in the 1960's. Today, switched outlets are found in modern homes built after 1995. Switched outlets are useful for connecting appliances that use different voltage levels; for example, an electric stove needs a 110-volt circuit to work properly, but other household electrical devices can be plugged into a 220-volt circuit. Outlets can also be found on telephones, wall clocks, and other small appliances that may be left on while they sleep but still need power to work. Outlets provide both safety and cost savings because they don't need separate wiring for each appliance.
Switch boxes are containers used to hold and protect individual switches while they're being installed in a building structure. A single switch may control several lights from one switch box. Light switches are available as single-pole, double-throw (SPDT) or three-way switches. Three-way switches are required by code for any place where there is more than one source of heat or air conditioning.
Superior grade materials, such as plastic and polycarbonate plastic, should be used to build switches and sockets that give standard functioning. The switches and sockets should be designed to be flexible, have minimal power consumption, and be functionally safe. Functional safety means that the device will perform its basic function in a correct manner under normal conditions. It may not operate properly if exposed to excessive heat or intense light intensity, for example.
The most common type of switch is the mechanical switch. This is constructed from two cooperating parts which can either both move or only one move depending on the position of the switch. Mechanical switches are available as rocker, push-pull, slide, and toggle types. Rocker and push-pull switches use a rotating shaft with holes at different locations around its circumference. When the hole in the center is aligned with the opening, the switch is in the "off" position. If no hole is aligned with the opening, the switch is in the "on" position. Slide and toggle switches work on a sliding mechanism where one part slides along another to change positions. They are generally more durable than rocker switches but they cannot be used with adhesive tape because the pressure needed to activate them would remove the tape from the surface it is attached to.
Electrical switches are used in many applications where a user-controlled on/off action is required.
(a) Electric plugs, switches, and plug boards are composed of thermosetting plastic, which is a poor electrical conductor. Such polymers do not conduct electric current. They retain their shape under pressure and do not break down over time.
(b) Plastic switches and plugs are easy to make because they only need to be molded in one piece. This is different from metal switches and plugs which must be formed by cutting or punching sheets or plates.
(c) Thermoset plastics do not corrode like metals do. This makes them ideal for applications where contact with water is likely.
(d) Thermoset plastics are very stable in high temperatures, which is important for things like switch covers and socket outlets.
Electricity is the flow of electrons through a conductor such as a copper wire. When these wires are joined together to form a circuit, they must be done so safely. If an electric circuit has any open spots or gaps, electricity will have nowhere to go when it flows through the circuit, causing serious damage to the items connected to the circuit. Items connected to an electric circuit can become hot due to the resistance of the metal inside them. This is why heat sinks are used with electronic devices to keep them from heating up too much.