Which switch type is classified as Normally Closed when used as a pushbutton?

• A. Pushbutton N.O.
• B. Pushbutton N.C.
• C. Pressure Switch N.O.
• D. Float Switch N.O.

Answer: (B)

The designation of a switch as "Normally Closed" refers to its default state in the absence of an external force, such as when the button is not being pressed. A pushbutton classified as Normally Closed, or N.C., means that the circuit is completed (current can flow) when the button is not pressed. When the button is actuated, this state changes, and the circuit opens (current is interrupted).

In the context of the choices presented, a pushbutton N.C. is specifically designed to allow current to pass through it until it is pressed. This characteristic is utilized in applications where it is desirable for a system to remain active until a user intentionally interrupts the circuit by pushing the button.

Recognizing the function of Normally Closed switches is crucial in automation and control systems, as it directly influences how devices respond to user interactions.