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10.4 Heat and Work in thermodynamics

Heat and work in thermodynamics are two distinct but mutually related concepts.


Heat is a form of energy which spontaneously flows from the hotter body to the colder one due to temperature difference.

As a result there is an increase in the temperature of the colder body.


However, temperature of a system or object may also be raised by performing work on it. For example, if we rub our hands together, we feel the warmth. This means the temperature of our hands has increased. 

Unlike the previous method, no temperature difference was involved between our hands and the temperature raise was not spontaneous. In fact, the work done against the friction between our hands appeared as raise in temperature.

Therefore, both work and heat can increase the temperature of an object.

(1) If it is spontaneous and difference in temperature is involved, the raise in temperature is due to heat.

(2) If work is exchanged between an object (or system) and surroundings (or other object) by the overall displacement of the object, the raise in temperature is due to work.


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