What do NO and NC indicate in pushbutton contacts?

What do NO and NC indicate in pushbutton contacts?

• A. NO means contact opens on actuation; NC means contact closes on actuation; momentary returns to its original state; maintained remains actuated.
• B. NO means contact closes on actuation; NC means contact opens on actuation; momentary stays engaged after actuation.
• C. NO means contact closes on actuation; NC means contact opens on actuation; momentary returns to original state; maintained remains actuated.
• D. NO stands for non-operational; NC stands for normally closed with no operation.

Answer: (C)

The concept being tested is how normally open and normally closed contacts behave in pushbuttons. Normally open means the contact is open when the button isn’t pressed; pressing the button closes that contact and completes the circuit. Normally closed means the contact is closed when the button isn’t pressed; pressing the button opens that contact and breaks the circuit. The terms momentary and maintained describe what happens after actuation: a momentary contact returns to its original state when you release the button, while a maintained contact stays in the actuated state until you actively reset it. So when you actuate the button, the normally open contact closes and the normally closed contact opens. If the pushbutton is momentary, these changes revert when you release; if it’s maintained, the changes stay until another action toggles them. This is why the correct description is that NO closes on actuation, NC opens on actuation, momentary returns to the original state, and maintained remains actuated.

The concept being tested is how normally open and normally closed contacts behave in pushbuttons.

Normally open means the contact is open when the button isn’t pressed; pressing the button closes that contact and completes the circuit. Normally closed means the contact is closed when the button isn’t pressed; pressing the button opens that contact and breaks the circuit. The terms momentary and maintained describe what happens after actuation: a momentary contact returns to its original state when you release the button, while a maintained contact stays in the actuated state until you actively reset it.

So when you actuate the button, the normally open contact closes and the normally closed contact opens. If the pushbutton is momentary, these changes revert when you release; if it’s maintained, the changes stay until another action toggles them. This is why the correct description is that NO closes on actuation, NC opens on actuation, momentary returns to the original state, and maintained remains actuated.