Second Law of Thermodynamics

This law states that “It is impossible for self acting machine, unaided by any external agency, to convey heat from a body at lower temperature to a body at a higher temperature“ i.e., heat cannot, by itself, pass from a colder body to a hotter body. Heat can be forced to pass to a higher temperature as in the action of a refrigeration machine
but only by applying an external agency to drive the machine.