This document discusses relays, including their construction, symbol, types, and advantages. A relay is an electromagnetic switch that uses a small electric current to turn on or off a larger current. It has a coil that becomes a magnet when powered, and uses this magnetism to switch contacts like normally open (NO) and normally closed (NC). Relays have multiple poles and throws to control connections. They allow low-power control of high-power loads, and are used in applications like motor control. Relays provide advantages like low control power requirements and switching of larger loads.

1. Relays
Prepared by Atheena Pandian

2. PRSENTATION
OVERVIEW
POINTS FOR DISCUSSION
What is Relay?
Electronic symbol
Pole and Throw
Construvtion
Simple Circuit Diagram
Types
Advantages
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3. WHAT IS
RELAY?
A relay is an electromagnetic switch operated by a
relatively small electric current that can turn on or off a
much larger electric current.
The heart of a relay is an electromagnet (a coil of wire that
becomes a temporary magnet when electricity flows
through it).

4. Symbol
A single pole
switch is often
denoted by
the letters SP,
and a double
pole by
DP. Relays can
have one, two
or more poles.
Common
Normally Normally
closed open

5. Throw and Pole
The pole of a relay is the terminal common to every
path. Each position where the pole can connect is
called a throw.
Throw: The number
of throws on an
electrical switch is
the number of
positions that are
available. For an
electromechanical
relay, there are
normally only one or
two throws.

6. CONSTRUCTON
Relay basically has a coil, to be specific
switching coil which switches between
contacts of relays
It has two or more than two contacts, we will
consider relay with two contacts of which one is NO
(Normally open) while other is NC(Normally Closed).
And a contact termed as COM (Common).

7. WORKING PRINCIPLE
It works on the principle of an electromagnetic
attraction.
When the circuit of the relay senses the fault
current, it energises the electromagnetic field
which produces the temporary magnetic field.
This magnetic field moves the relay armature for
opening or closing the connections.

8. Simple relay switch diagram

9. T
Y
P
E
S

10. The advantage of relays is
that it takes a relatively
small amount of power to
operate the relay coil, but
the relay itself can be used
to control motors, heaters,
lamps or AC circuits which
themselves can draw a lot
more electrical power.
Applications

11. Thank You