Saravh asked in Science & MathematicsEngineering · 1 decade ago

# what is relay (electrical term).....?where is it works???and what use?

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• iceman
Lv 7

An electrical relay is a switch which is under the control of another circuit. A classic example of an electrical relay is the system used to start a car. When someone turns an ignition key, the ignition does not interact directly with the car battery. Instead, it activates an electrical relay which passes the signal on so that the car can start.

• 1 decade ago

A relay is an electrically operated switch....

Relay(electromagnetic type) consists of a coil of wire surrounding a soft iron core, an iron yoke, which provides a low reluctance path for magnetic flux, a movable iron armature, and a set, or sets, of contacts...

When an electric current is passed through the coil, the resulting magnetic field attracts the armature, and the consequent movement of the movable contact or contacts either makes or breaks a connection with a fixed contact. If the set of contacts was closed when the relay was De-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open

• 1 decade ago

A relay is an electromechanical device that basically uses an electromagnet to throw a switch.

A relay consists of two parts, first a coil, that can be designed to operate on DC or AC or any voltage between 5 volts and 240 volts. Second, a set of contacts that are engaged by the coil. The contacts can vary from a simple NO (Normally open) or NC (Normally closed) contact that is closed (or opened) when you apply the correct voltage to the coil, to more complicated SPDT (single pole double throw) to 4PDT (four pole double throw) or even more complicated sets of contacts.

All of the contacts are isolated from each other and from the coil.

In size and capacity, they vary from tiny reed switches designed to switch small signals to huge contactors made to switch large currents for a motor.

There are also other varieties such as time delay relays, latching relays and more.

Another type is SSR, solid state relays, where the relay uses opto couplers and FET switches to simulate the action of a relay with faster speed and higher reliability.

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