For 20 points, name this law which most commonly states that heat never spontaneously flows from a cold source to a hot source.
One extension of this law states that the efficiency of a Carnot cycle is equal to the difference in temperature between the hot and cold reservoirs, divided by the temperature of the hot reservoir. One variant of this law states that one can never achieve 100% efficiency, while another variant states that the total entropy of the universe is increasing. For 20 points, name this law which most commonly states that heat never spontaneously flows from a cold source to a hot source.
One extension of this law states that the efficiency of a Carnot cycle is equal to the difference in temperature between the hot and cold reservoirs, divided by the temperature of the hot reservoir.
{Second} Law of {Thermodynamics}