Which statement correctly differentiates a relay from a high-current switch?

• A. A relay is a high-current control device that actuates a low-current circuit.
• B. A relay is a low-current control device that actuates a high-current circuit; a high-current switch directly controls heavy loads.
• C. They perform the same function.
• D. A relay only works with AC signals.

Answer: (B)

Relays separate the control and power paths: a relay uses a low-current coil to actuate high-current contacts, so a small control signal can switch a heavy load. The coil draws little current and can be powered from a different voltage than the load, providing isolation between the control circuit and the load circuit. The load current flows through the relay contacts, which are rated for high current, while the coil is separate from that path. A high-current switch, by contrast, handles the heavy current directly in the same path used to operate the load and does not provide the same level of isolation or indirect control. It may be manual or controlled, but it does not use a separate low-current control coil. Relays can be driven by DC or AC coils depending on design, so the coil type is not restricted to AC. Thus, describing a relay as a low-current control device that actuates a high-current circuit, while a high-current switch directly controls heavy loads, best captures the distinction.