In ladder diagrams, which element is represented by a relay coil symbol and controls an external output device?

In ladder diagrams, which element is represented by a relay coil symbol and controls an external output device?

• A. Coil
• B. Relay
• C. Contacts
• D. Timer

Answer: (A)

In ladder diagrams, the coil symbol represents the actuator that, when energized, drives an external device (through the relay’s contacts). When the rung conditions are met, current energizes the coil, which energizes the relay and causes its contacts to switch the external load on or off. So the coil is the element that implements the output control—the part that actually drives the external device. The other items describe the switching contacts (the load path), the relay itself as the device being driven, and timing hardware, which is a different function.

In ladder diagrams, the coil symbol represents the actuator that, when energized, drives an external device (through the relay’s contacts). When the rung conditions are met, current energizes the coil, which energizes the relay and causes its contacts to switch the external load on or off. So the coil is the element that implements the output control—the part that actually drives the external device. The other items describe the switching contacts (the load path), the relay itself as the device being driven, and timing hardware, which is a different function.