Hi Friends...Today i'm going to post about relay.In this post i will cover What is relay? Its types, parts which a relay consist,and about how a relay is working... As we all know Relay is a very important device now days.It used in various types of circuits our school project,university project as well as industry projects.And the purpose of this post is many of us have problems of how to use a relay. And in this post i will try to solve this problem. RELAY : A relay is an electrical switch actuated by an electromagnetic coil.And the main purpose of relay is switching. Types of relay 1. Single Pole Single Throw (SPST)- These types of relay provides one contact at a time it may be a normally open or normally close.These relays comprise of 4 terminals. Two terminals are used as coil points and other two can be used to connect or disconnect the circuit (A and B). 2. Single Pole Double Throw (SPDT...