Heat.
Heat is a form of energy that is always moving, he is traveling hottest at least warm. Heat is energy in transit is recognized only when the border is crossed a thermodynamic system. Once inside the system, or around, if the transfer is from the inside out, the heat transfer becomes part of the internal energy of the system or the surrounding area, as appropriate. The term heat, therefore, should be understood as heat transfer and only occurs when there is difference in temperature and direction from highest to lowest. It follows that no heat transfer between two systems that are in thermal equilibrium
Ways to transmit heat.
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Radiation: The way to transmit heat by gases or vacuum.
Driving: It is the way to transmit the heat from solid objects THROUGH preferred metals..