Lab Report Day 7 - Cycles and Efficiency

Stirring Engine:

A difference in temperature can make the stirring engine work. First, a hot water reservoir is put on the bottom with a beaker of water on a hot plate, and then a cold reservoir is placed on top, with ice cubes covered. Stirring engines have very low power. The use of solar energy is by using stirring engine. The sun provides heat which causes difference in temperature, thus the stirring engine works. In a stirring engine, energy is not being generated in form of mechanical work.

The set up of  stirring engine.

The efficiency of this engine is 27%.  However, it cannot be this high for the solar panel since the temperature difference is much smaller.

Power

We want to calculate man’s power of climbing stairs. We want to know how many floors a man need to climb in a minute in order to have the equivalent power as 1 horse power (760 W). We assume the man is 100 kg and one floor is about 5 meters.

He is measuring how high is one floor.

  We calculate that a man need to climb 9.30 floors in a minute in order to have 760 Watts of power. We can do that, but we cannot do it continuously while a horse can do it for hours. 

Conclusion

In today’s class, we learn what is entropy. We learn how to increase entropy. We learn that the difference in temperature can cause a stirring engine to work, and the efficiency of a stirring engine is not very high. We learn that what one horse power is equal to, and we learn how to calculate the efficiency of a heater/refrigerator.