Applications of the First Law of Thermodynamics (Continuation)

Applications of the First Law of Thermodynamics (Continuation)

The picture shown here were presented to see how adding some heat (positive, high temperature, or negative, low temperature) the device (the upper photo) can do work. Since the heat will go from one side to another (hottest to coolest), the rotational part will do work accordingly with how the heat flows. However, it also does work when it is applied negative heat, and the rotational part will rotate in the opposite direction.

The second works almost the way as the first picture, but just when positive heat is added. Once heat is added, the seringy will start going up because work is been done by the gas to its surroundings, which will expand and increasing the volume of it. To compress the gas, the heat source is pulled over and and the surroundings will do some work on the gas. This can be used to lift a reasonable mass, like an apple.

This picture shows the full cycle of a heat engine. The process the this engine passes through are Isothermal (constant temperature) and Isobaric (constant pressure). Here students were asked to find the network for the interi cycle, which would be the area of the figure. 

This two pictures represent the process of a heat engine and its calculations for internal energy, heat in and out (Qh, Qc) and its efficiency. In this case the engine were considered to be ideal. 

The conclusion about the applications of the first law of thermodynamics gave to students a better understanding about an engine cycle. Although the ones used by students were considered ideals, the are made to make studies in how an engine will behave in the real world, where all the heat that goes to the engine will be divided in work and some of them will be lost and never recovered. It is also a way to see how, in an ideal conditions, an engine can be highly efficient. Nonetheless, this efficiency is never applied to the real world because the heat that goes to the engine, will never be totally recovered. Some will do work and some will be lost, but just a portion of it is again reused to repeat the cycle again.