<P> Heat is the amount of energy flowing from one body of matter to another spontaneously due to their temperature difference, or by any means other than through work or the transfer of matter . The transfer can be by contact between the source and the destination body, as in conduction; or by radiation between remote bodies; or by way of an intermediate fluid body, as in convective circulation; or by a combination of these . In thermodynamics, heat is often contrasted with work: heat applies to individual particles (such as atoms or molecules), work applies to objects (or a system as a whole). Heat involves stochastic (or random) motion equally distributed among all degrees of freedom, while work is directional, confined to one or more specific degrees of freedom . </P> <P> Since heat (like work) represents a quantity of energy being transferred between two bodies by certain processes, neither body "has" a definite amount of heat (much like a body in itself doesn't "have" work); in contrast, a body indeed has properties (state functions) such as temperature and internal energy . Thus, energy exchanged as heat during a given process changes the (internal) energy of each body by equal and opposite amounts . The sign of the quantity of heat can indicate the direction of the transfer, for example from system A to system B; negation indicates energy flowing in the opposite direction . </P>

Which method represents the transfer of heat in a fluid