You need to prepare to perform a First Law analysis on a device. The device is covered in insulation, and appears to have a plunger on the top which can move up and down during operation. There are also electrical wires entering and exiting the walls of the device. The device appears to be sealed. Beginning with the general equation for the First Law of Thermodynamics, develop a simplified expression that should be suitable for use with this device to calculate the overall behavior of this device for a period of time.
What will be an ideal response?
From the information given and observations, the following can be assumed:
(1) The device is a closed system, as it is sealed.
(2) The insulation suggests that there is no heat transfer.
(3) The plunger suggests that there is moving boundary work, and the electrical wires
suggest that there is electrical work – therefore, the work should not be ignored.
(4) The device is likely stationary, so kinetic and potential energy changes can be
neglected.
Therefore, starting with the First Law for closed systems:
we can assume that Q = ?ke = ?pe = 0, leaving
W = m (u1 – u2)
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What will be an ideal response?