Transformer:

Transformers are two coils of wire linked usualy by an iron core. Energy is transferred between the coils by the magnetic field in the core.  Transformers are used to step up (increase) and step down (decrease) AC voltages. For example a transformer may be supplied with 110 volts AC and produce a voltage of 3 VAC or 2000 VAC. A transformer does notgenerate electricity it increases or decreases a circut’s voltage.

Diode:

A diode is an electrical device that only allows current to flow in one direction, like a one way gate. In a microwave oven diodes are used in line with a transformer and capacitor to create a large voltage discharge used by the microwave’s magnetron to create the microwaves used to excite the water in your food.

Capacitor:

A capacitor stores an electric charge.  (Notethat that electrical charge can remain even after a circuit’s power supply has been removed or unplugged!)

Ground or Earth Connection:

This connection is very important; it is usually made with bare wire attached to the cabinet of an appliance, which is in turn connected to earth within the service panel of your home through a “grounded” plug. This connection serves a safety protecting against electrocution in the case of a short.

Switches:

Terms describing switch properties

Open:

Off position, offering infinite resistance to a circuit.

Closed:

On position, offering zero resistance to a circuit.

Pole:

Number of contact sets.

Throw:

Number of conducting positions. (Single or double)

Way:

Number of conducting positions. (Three or more)

Momentary:

A switch that returns to its normal position when released.

Types of switches

On-Off Switch SPST:
(Single Pole, Single Throw)

An on-off switch allows current to flow only when it is in the closed or on position.

2-Way Switch SPDT:
(Single Pole Double Throw)

A 2-way switch directs the flow of current to one of two routes according to its position. Some SPDT switches have a central off position.

Relay:

A relay is an electrically operated switch, commonly used in appliance control boards.

Pressure sensing switch:

This style of switch has a pressure sensing mechanism inside it, usually a diaphragm, which flexes as pressure increases and opens or closes a switch as the pressure reaches a specific level. These switches are commonly used in washing machines to sense the amount of water that has entered the washtub and prevent overflow.

Push to Make Switch:

A push to make switch allows current to flow when the switch is pressed.

Push to Break Switch:

This type of push switch is normally closed (on) it is open (off) only when the button is pressed.

Dual On-Off Switch DPST
(Double Pole Single Throw):

A dual on-off switch.Two switches that open and close at the same time.

Reversing Switch DPDT
(Double Pole Double Throw):

This switch can be used to change the direction of a motor.