# Condition for increase in internal energy of system - Thermodynamics

Q.  When the heat transfer into a system is more than the work transfer out of the system, then
- Published on 19 Aug 15

a. the internal energy of the system remains constant
b. the internal energy of the system decreases
c. the internal energy of the system increases
d. none of the above

ANSWER: the internal energy of the system increases

When a system undergoes cycle, then the algebraic sum of all energy transfer across the boundaries is zero. But when a system undergoes a change of state in which both heat transfer and work transfer are involved, the net energy transfer is stored and collected within the system. If Q is the amount of heat transferred to the system and W is the amount of work transferred from the system during the process, then the net energy (Q – W) is stored in the system. This energy is neither heat nor work but it is called as internal energy. As the heat transfer is more that work transfer then the internal energy (ΔE) increases.
Q – W = ΔE

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