What occurs when the galley heating system is activated?

When the galley heating system is activated, the primary function is to warm the food and beverages. This system is designed to ensure that in-flight meals and drinks are heated to appropriate temperatures for passenger service. It utilizes elements within the galley equipment that provide direct heat to warm these items efficiently during flight operations.

The other possibilities, such as cooling down the cabin, activating emergency lights, or draining potable water, are not associated with the galley heating system's purpose. Cooling the cabin is typically managed by the aircraft’s climate control systems. Emergency lights are activated under specific safety protocols, and potable water systems operate independently from the galley heating functions. Thus, the confirmation that the correct answer is the warming of food and beverages aligns precisely with the intended operation of the galley heating system.