# Consequences of energy transfer

A radiator does radiate some: heat, and if you stand near a hot radiator your hands can feel the infrared radiation being emitted by the front surface of the radiator. However, this is only around one quarter of the heat being released by the radiator. Three quarters of the heat is taken away by the hot air that rises from the radiator. Colder air from the room flows in to replace this hot air, and convection current is formed.

You will note that the convection current is far more efficient at heating the top of the room than it is at heating the person standing in front of the radiator.

The vacuum flask works j ust as well t he other way, at keeping the contents cool. And in fact it was invented in the 1890s by a Scottish physicist so that he could keep liquefied gases, such as liquid hydrogen that boils at $-250^{0}C$. Scientists usually call it a Dewar flask in his honour.