What device is an electrically operated switch that may operate multiple switches at one time, with a coil creating a magnetic field to move the contacts?

• A. Resistor (nonvariable)
• B. Two-way switch
• C. Relay (relay switch)
• D. Dual on/off switch

Answer: (C)

Relays are electromagnetically operated switches. They have a coil that, when energized, creates a magnetic field which pulls the contacts to open or close. This lets a small control current move one or more circuits at once, since relays can be built with multiple contact sets to operate several switches simultaneously. The other options don’t fit because a resistor is a passive component that doesn’t move contacts, a two-way switch is a manual selector with no coil, and a dual on/off switch is simply two manual switches rather than a coil-driven mechanism that can control multiple circuits.