An electrically operated control requires 24 volts to operate. To reduce 110 volts to 24 volts you will need:

• A. Resistor divider
• B. Inverter
• C. Transformer
• D. Relay

Answer: (C)

To power a 24V control from a 110V line, you need a device that steps down AC voltage while providing isolation. A transformer does this by having a primary winding on the 110V side and a secondary winding that delivers 24V, with the output set by the turns ratio and rated for the required current. The power in roughly equals the power out, minus small losses, so the control gets a stable supply as long as the transformer is correctly rated. A resistor divider wastes power as heat, varies with load, and offers no isolation, making it unsuitable for powering a real control circuit. An inverter converts DC to AC, not used for reducing AC voltage directly. A relay is just a switch and does not change voltage levels.