Physics - Ch. 13

Terms to Know

100

What objects convert thermal energy into mechanical work?

Heat engine

200

In all processes, _____________ must increase or remain the same.

Entropy

300

What does a heat pump do?

Does work to move thermal energy from a cold reservoir to a hot reservoir

Reverses the Carnot cycle

400

Describe the four steps of the Carnot Cycle.

The system absorbs thermal energy (Q_H) from the hot reservoir.

The system expands adiabatically (work is done on the piston)

The system gives up thermal energy (Q_C) to a cold reservoir.

 

The gas adiabatically compresses further

500

State the Four Laws of Thermodynamics

Zeroth - If two systems are in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other

First - Energy cannot be created or destroyed, only transferred or transformed

Second - Thermal energy flows from an area of higher concentration to an area of lower concentration

Third - absolute zero is unattainable

Solving

100

Which system cannot exchange energy nor matter with its surroundings?

Isolated system

200

350 J of work is done on a system.   90 J of thermal energy is lost by the system.  What is the change in internal energy of a system?

260 J

300

A heat engine has a cold reservoir at 974 ^oC.  If the efficiency is 49%, what is the temperature of the hot reservoir?

1909 ^oC

400

A gas at 45 L and 399 Pa expands to 90 L and 200Pa.  What is the work done? Is it on or by the gas?

13477.5 J

Work is done by the gas

500

A gas is used to move a piston.  Originally, the gas is at 15 L and 400 Pa.  Then, the volume is decreased to 3 L and the pressure is increased to 1000 Pa.  Then, the pressure decreases to 400 Pa while keeping the volume the same at 3 L.  Finally, the volume expands to 15 L while keeping the pressure at 400 Pa.  What is the work done?  Is it on or by the gas?

3600 J

Done on the gas