1. 2nd Law of Thermodynamics
Higher Temperature
Lower Temperature
Heat
Heat will not flow spontaneously from a lower temperature object to a higher temperature object.

2. Heat Engine – any device that uses heat to do workQH
(input heat)
Conservation of Energy:
QH = W + QC
W (Work) QC
(rejected heat)

3. hyperphysics

4. An engine has an efficiency of 20% and produces 2000 J of mechanical work during one cycle. How much energy is transferred out of the engine by heating the environment during one cycle?
100 J
2000 J
8000 J
10000 J

5. Th= 550 K Tc
Engine Qh Qc W
= 630 J
= 920 J
For the engine
a) What is the Work done by engine each cycle?
b) What is the efficiency of the engine?

6. hyperphysics

7. Refrigerators, Air Conditioners and Heat Pumps
For these, we need heat to flow from lower to higher temperature:
This requires work
Conservation of Energy:
QH = W + QC