He remembered he hadn't turned on either the heating element or interphone system.
The heating element is brought close to the top of the battery.
Convection warms food in pans that are not actually touching the heating element.
The heating element must be fastened to the mug with a clamp.
Conduction occurs when you set a pan containing food right on a heating element.
The bottoms of these mugs have a flange which makes a recessed part and in this the heating element is placed.