# 1st Law for Transient Processes

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## Transient Process

(or unsteady process) :A process in which one or more properties or process variables change as a function of time.

Transient processes can be very complex. Therefore, we will only consider processes in which we can assume uniform flow and uniform state.

In the previous lesson, we saw how much the uniform flow assumption simplified the differential mass balance equation. In this lesson, we will see how much the uniform flow and uniform state assumptions simplify the differential form of the 1st Law.

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