In ladder logic, what does a normally open (NO) contact represent?

In ladder logic, what does a normally open (NO) contact represent?

• A. It represents a switch that closes the circuit when the input is true.
• B. It represents a switch that opens the circuit when the input is true.
• C. It represents an always-closed contact.
• D. It represents an output coil.

Answer: (A)

In ladder logic, a normally open contact starts open and makes a path only when its input is true. When the input condition becomes true (like a pressed start button or an activated sensor), the contact closes and current can flow through that rung to energize the next element, such as an output coil. This behavior—closing the circuit when the input is true—is why it’s described as normally open. It’s not always closed, not an output coil, and not a contact that opens on true.

In ladder logic, a normally open contact starts open and makes a path only when its input is true. When the input condition becomes true (like a pressed start button or an activated sensor), the contact closes and current can flow through that rung to energize the next element, such as an output coil. This behavior—closing the circuit when the input is true—is why it’s described as normally open. It’s not always closed, not an output coil, and not a contact that opens on true.