Which component is used to open or close a circuit and can be normally open or normally closed?

• A. A capacitor
• B. A resistor
• C. A switch
• D. A diode

Answer: (C)

A switch is used to open or close a circuit. Its job is to complete or interrupt the electrical path so current can start or stop flowing to a device. When a switch is normally open, there is no connection at rest, and actuating it closes the contacts to allow current to flow. When a switch is normally closed, there is a complete connection at rest, and actuating it opens the contacts to stop current. This distinction helps you control circuits in different ways—for example, a light switch is typically normally open so flipping it on creates a closed path to light the lamp, while some safety interlocks use normally closed configurations so the circuit opens if something changes. Other components like a capacitor, resistor, or diode don’t provide a controllable on/off path in the way a switch does: a capacitor stores charge and may affect current temporarily, a resistor merely limits current, and a diode controls current direction but doesn’t switch the circuit on or off.