Qualifying Exam

The forebay of a dam feeds 900 Mg/s of water to an electrical generating plant. The water has a specific volume of 0.001 m³/kg. It enters the generators at 900 kPa and leaves at 200 kPa. Kinetic and potential energy changes are insignificant. The water’s temperature is constant. What is most nearly the power generated by the dam?

180 MW
630 MW
810 MW
900 MW

Which of the following principles is the closest interpretation of the first law of thermodynamics for a closed system?

The mass within a closed control volume does not change.
The net energy crossing the system boundary equals the change in energy inside the system.
The change of total energy is equal to the rate of work performed.
All real processes tend toward increased disorder.

What is the origin of the energy conservation equation used in flow systems?

Newton’s first law of motion
Newton’s second law of motion
the first law of thermodynamics
the second law of thermodynamics

Steam flows into a turbine at a rate of 10 kg/s, and 10 kW of heat are lost from the turbine.

	inlet conditions	exit conditions
pressure	1.0 MPa	0.1 MPa
temperature	350°C	–
quality	–	100%

Elevation and kinetic energy effects are negligible. What is most nearly the power output from the turbine?

4000 kW
4400 kW
4800 kW
5000 kW

For which type of process is the equation valid?

irreversible
isothermal
reversible
isobaric

What does the dashed curve in the state diagram represent?

the solidus curve
an isotherm
the saturated liquid curve
the saturated vapor curve

A three-dimensional phase diagram for a pure substance is shown.

The state of a sample of the substance is constrained by its conditions to the dotted curve but not the endpoints. How many degrees of freedom does the system have?

0
1
2
3

Which of the following is a proper statement of the second law of thermodynamics?

It is impossible for a heat engine to produce network in a complete cycle if it exchanges heat only with bodies at a lower temperature.
It is impossible for a system working in a complete cycle to accomplish, as its sole effect, the transfer of heat from a body at a given temperature to a body at a higher temperature.
It is impossible for a system working in a complete cycle to accomplish, as its sole effect, the transfer of heat from a body at a given temperature to a body at a lower temperature
It is impossible for a heat engine to produce net work in a complete cycle if it exchanges heat only with bodies exhibiting a temperature differential.

Air at 1 MPa and 400K expands through an adiabatic turbine operating at steady state to 0.15 MPa and 320K. Changes in kinetic and potential energies are negligible, and air is an ideal gas with constant specific heats of 0.7165 kJ/kg·K (constant volume) and 1.0035 kJ/kg·K (constant pressure). The surrounding environment is at 101.3 kPa and 298.15K.

Most nearly, what is the maximum work?

120 kJ/kg
160 kJ/kg
180 kJ/kg
210 kJ/kg

Which of the following system condition(s) can be considered to have responses that increase entropy?

ideal expansion waves
ideal shock waves
natural chemical reactions occurring spontaneously

1 Only
1 and 2
1 and 3
2 and 3

Semiconductor and 2D Material

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Participants 16

Qualifying Exam

Abdulaziz June 25, 2021

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