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1 When the burner of a stovetop is very hot, it is a source of heat energy. 2  Anything placed onto the stovetop and warmed, whether a pot of tea or a skillet for frying eggs, also become sources of heat energy. 3  Automobile fuels such as gasoline are sources of heat energy, as is the hot engine of a racecar or a school bus.
The earth's core is divided into two separate regions: the liquid outer core and the solid inner core, with the transition between the two lying at a depth of 5,156 kilometers (3,204 miles).here are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.