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Question
Explain given cases related to energy transfer between the system and surrounding –
- energy transferred (Q) > 0
- energy transferred (Q) < 0
- energy transferred (Q) = 0
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Solution
Consider a system with temperature TS is kept in an environment of temperature TE. Let Q be the energy transferred between the system and the environment.
- When the temperature of the system is less than that of the environment (TS < TE), the energy flows into the system as shown in figure (a).
TS < TE
As a result, the system gains energy and Q is positive. - When TS > TE, the system loses energy i.e., the energy flows from the system into the environment as shown in figure (b).
TS > TE
In this case, Q is negative. - For TS = TE, as shown in figure (c), the system and the environment are in thermal equilibrium and there is no transfer of energy i.e., Q = 0.
TS = TE
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