In ladder logic, what does a normally open (NO) contact represent and when does it conduct?

In ladder logic, what does a normally open (NO) contact represent and when does it conduct?

• A. It represents a condition that conducts when the contact closes (when the associated coil or condition is true).
• B. It conducts only when the coil is energized, regardless of the contact status.
• C. It always conducts regardless of input.
• D. It never conducts.

Answer: (A)

A normally open contact behaves like a switch that is open by default and will close when its controlling input becomes true. When it closes, it forms a conducting path and current can flow through the rung to energize the next element (like a coil) or continue the logic. This mirrors a physical NO pushbutton: nothing happens until you actuate it, at which point the circuit is completed and current flows. So the contact conducts only when it closes—that is, when the associated input or coil is energized/true.

A normally open contact behaves like a switch that is open by default and will close when its controlling input becomes true. When it closes, it forms a conducting path and current can flow through the rung to energize the next element (like a coil) or continue the logic. This mirrors a physical NO pushbutton: nothing happens until you actuate it, at which point the circuit is completed and current flows. So the contact conducts only when it closes—that is, when the associated input or coil is energized/true.