In a motor control circuit, a device used to open and close the motor circuit under load is commonly a:

• A. Line starter
• B. Push button
• C. Contactor
• D. Pilot lamp

Answer: (A)

Opening and closing the motor circuit while the motor is under load requires a switch that can safely handle the high current and arcing that occur during starting and stopping. A line starter is designed for this role: it provides the main contacts that connect or disconnect the motor from the power supply and typically includes overload protection to guard the motor during starting and running. The control side (like a push button) merely energizes the line starter’s coil; it does not carry the motor current itself. A pilot lamp is only an indicator and does not switch the motor circuit. While a contactor is the device that carries motor current, the line starter describes the complete line-side switching assembly used to open or close the motor circuit under load, making it the best answer in this context.