1.1.5. a -e Heat Engines and Efficiency

A refrigerator removes a quantity of energy as heat from inside the refrigerator and transfers this energy to the air outside the refrigerator. Which statement correctly describes how this is done?

• Work is done on the system so that energy can be transferred as heat from a low temperature to a high temperature

• Work is done by the system so that energy can be transferred as heat from a low temperature to a high temperature.

• Energy is transferred as heat spontaneously from the high temperature inside the refrigerator to the low temperature outside.

• Energy is transferred as heat spontaneously from the low temperature inside the refrigerator to the high temperature outside.

What type of energy represents the sum of the KE and PE that a moving object has?

• chemical energy
• total mechanical energy
• electromagnetic energy
• electrical energy

The heat energy coming out of the hot reservoir, Q H , into the system (engine) is 200 J. The energy that goes out of the system into the cold reservoir, Q C , is 150 J of waste heat. In joules, how much work was done by the system?

If the heat energy from the hot reservoir is 60 J and the waste energy is 10 J, calculate W_out using the formula: W = -Q_net

• -70 J

• 70 J

• -50 J

• 50 J

• 100%

• 80%

• 40%

• 10%

What is the efficiency of an engine that absorbs 200 J of heat and performs 50 J of work?

• 25%

• 50%

• 75%

• 100%

If heat added to the cycle is 40 kJ and the one rejected is 20 kJ then the efficiency of the cycle will be

• 40%

• 50%

• 60%

• 100%

In a heat engine, 750J is drawn from the hot reservoir, and 400J is released to the cold reservoir.

How much work is done by the engine?

• 300 J

• 350 J

• 1150 J

• 0

A heat engine does a work of 220J when receiving 600J of heat. How much energy is emitted through the exhaust?

• 380 J

• 820 J

• 480 J

• 880 J

A heat engine does 100 J of work, and emits 100 J to the cold reservoir. What is the efficiency of the engine?

• 50%

• 33%

• 20%

• 100%