Why cant heat travel from the grill to toast by convention?

Answer 1

Conduction is the process of heat diffusing through a substance that conducts heat. The less conductive the substance is (like glass, air, or an oven glove), the slower the conduction is. Convection is the movement of heat that occurs when a mass of hot substance physically moves to another location. Both of these mechanisms depend on the presence of a material substance to move heat from place to place, and the efficiency of the mechanism depends on the characteristics of the substance. Radiation is the movement of heat in the form of electromagnetic radiation. It doesn't require any substance in the intervening space to transfer the heat; in fact, it is most efficient when there is NOTHING in the way. That's how heat reaches us from the sun.