Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is Normally Closed (NC), there is a closed contact when the relay is not energized.
Correspondingly, what does normally closed and normally open mean?
Normally Open/Closed. When a momentary switch is not actuated, it's in a “normal” state. Depending on how the button is constructed, its normal state can be either an open circuit or a short circuit. When a button is open until actuated, it's said to be normally open (abbreviated NO).
What does it mean when a relay is normally open?
An electrical contact is an electrical circuit component found in electrical switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, usually metal. When the contacts touch, the switch is "closed"; when the contacts are separated, the switch is "open".
What is a normally open circuit?
An "open" circuit is an incomplete circuit, with "open space" between contacts. Therefore a normally open circuit can also be referred to as "normally OFF". A normally closed or N.C. momentary switch has one or more circuits that are closed when the switch actuator is at its normal or rest position.