magnetism and electromagnetism

Relay

An electrically operated switch that uses an electromagnet to mechanically operate a switch, controlling high-power circuits with low-power signals.

Electromagnet Coil

A coil that generates a magnetic field when current flows through it, with strength dependent on the number of turns in the coil and the current flowing.

Armature

The moveable portion of a relay, a ferrous piece attracted by electromagnetic force, which pivots to make or break contact.

Contacts

Switching elements of a relay, made of conductive material, that open or close to control the flow of current.

Normally Open (NO) Contacts

Contacts that are open when the relay coil is de-energized and close when the coil is energized.

Normally Closed (NC) Contacts

Contacts that are closed when the relay coil is de-energized and open when the coil is energized.

Changeover/Double-Throw (CO or DT) Contacts

Contacts that include both NO and NC, allowing a switch between two different circuits.

Spring in Relay

A component that provides a restoring force to return the armature to its original position when the current to the coil is removed.

Single Pole Single Throw (SPST)

A relay type that has one input terminal and one output terminal, acting as a simple on/off switch.

Single Pole Double Throw (SPDT)

A relay type that has one common input terminal and two output terminals, able to switch current to one of two paths.

Double Pole Single Throw (DPST)

A relay type that has two input terminals and two output terminals, functioning as two SPST relays controlled by a single coil.

Double Pole Double Throw (DPDT)

A relay type with two input terminals and four output terminals, which acts as two SPDT relays controlled by a single coil.

Principles of Magnetism

Concepts that explain how electromagnets create magnetic fields and how magnetic domains behave in materials.

Permanent Magnets

Magnets that retain their magnetism without an external magnetic field and can be damaged by strong opposing fields or heat.

Domain Theory of Magnetism

Explains magnetic behavior in materials where domains align under an external magnetic field, leading to magnetization.

Ceramic Magnets

Hard, brittle permanent magnets made of ceramic materials, commonly used for strong magnetic fields in various applications.

Applications of Relays

Widely used in motor control, automotive systems, industrial automation, HVAC systems, telecommunications, and home appliances.