Thermodynamics Reading Quizzes (#2)

Which of the following statements are true regarding the similarities between heat and work?

-both heat and work are path functions -both heat and work can cross the boundary of a system -both heat and work are associated with a process NOT: -both heat and work are associated with a thermodynamic state -systems possess energy including heat and work

Select all of the mechanisms of heat transfer from the list below

-conduction -convection -radiation NOT: -evaporation

Select all of the following that represents units for a rate of heat transfer******

-kW

Which following energy forms of system are microscopic?

-latent energy -sensible energy -nuclear energy NOT: -electrical energy -potential energy of the system

Which of the following energies are not microscopic?

-mechanical energy NOT: -sensible energy -chemical energy -latent energy -nuclear energy

Energy can exist in many forms. Which of the following is an energy form?

-potential -kinetic -chemical -electrical NOT: -temperature

Which energy forms of the following is macroscopic?

-potentital energy -electrical energy -kinetic energy NOT: -intermolecular binding energy -internal energy

Which of the following statements are true?

-sulfur in fossil fuel reacts with oxygen and then dissolves in water vapor to form sulfuric acid in our atmosphere, which causes acid rain -the undesirable consequences of the greenhouse effect cause global warming -smog is made up mostly of ground-level ozone, but it also contains numerous other chemicals such as carbon monoxide, soot, and dust -carbon dioxide is considered as the primary component of the greenhouse gases NOT: -the current concentration of CO2 in the atmosphere is about 40 ppm

Select all of they ways in which a process can be adiabatic.

-the system is well insulted -the system is at the small temperature as the surroundings NOT: -the system does not change temperature during the process -no work crosses the system boundary

There are two requirements for a boundary work interaction between a system and its surroundings to exist. Select the two answers that are correct.

-there must be a force acting on the boundary -the boundary must move NOT: -the boundary must be insulated -there mist be an internal, not external force, applied within the system's boundary -the boundary must be imaginary

For a cooking appliance, the overall energy supplied to the appliance is 5 kWh and only 4 kWh is transferred to the food. What is the appliance's efficiency?

0.8

A power plant produced 36000 kJ of work in an hour. How much power did it produce?

10 kW (Power = Work/Time)

A potato is baked in an oven. Considering that any moisture loss from the potato is disregarded and the oven is well insulated, if 2 kJ of heat is transferred to the potato, what is the energy change of the potato?

2 kJ

10 kJ heat is transferred to control volume and 7 kJ work is done by the control volume. Some mass also enters or leaves the system. If the energy change of the system is zero, the energy of the mass entering or leaving the system is...

3 kJ out

A linear spring with spring constant k=300 N/m is stretched until it is 100 mm longer. Find the required force and work.

30 N, 1.5 J

A process requires heat addition at a constant rate of 100 kW for 60 seconds. In order to add an equivalent amount of heat in 20 seconds, what rate of heat transfer would be required?

300 kW (100 kW)(60 s) = 6000 kJ and (300 kW)(20 s) = 6000 kJ

Heat is added to a system to raise its temperature 10°C in 20 minutes. If the rate of heat transfer were cut in half, how long would the process have to run in order to transfer an equivalent amount of heat?

40 minutes (amount of heat = the rate of heat transfer x time)

8 kW of shaft work is done on a system while 3 kW of heat is lost from the system. Whats is the rate of energy change of the system?

5 kW (W[in] - Q [out] = change in energy of the system)

The torque applied to the shaft of a car is 180 Nm and the shaft rotates at rate of 300 rpm. What is the power transmitted through the shaft?

56.52 kW (W[sh] = (2πnT)/60, where n is the number of revolutions per minute and T is torque)

Heat and work are point functions.

False

Match the heat transfer dimensions on the left with their corresponding units on the right.

Heat transfer: kJ Heat transfer per unit mass: kJ/kg Rate of heat transfer: kW

Following the formal sign convention, please match the heat and work interactions with their appropriate signs:

Positive: -work done by the system -heat transfer into the system Negative: -heat transfer out of the system -work done to the system

In 1997, the world's industrialized countries adopted the Kyoto protocol and committed to reduce by 2008 to 2012 their CO2 and other greenhouse gas emissions by 5% below the 1990 levels.

True

___ is the transfer of energy between a solid surface and the adjacent fluid that is in motion

convection

The electrical power equals the square of the ___ multiplying the resistance.

current

The phrase of global warming indicates that some form of net energy has been created.

false

We are told repeatedly that energy can neither be created nor destroyed; it can only change forms. This statement is also referred to as the...

first law of thermodynamics

Work is the energy transfer associated with ___ acting through a distance

force

An adiabatic process is one in which there is no...

heat transfer

When mass enters a system, the energy in the system...

increases

The internal energy that is required to undergo a phase transition and is associated with the binding forces between the molecules of a substance is called ___ energy.

latent

Efficiency can be expressed in terms of the desired ___ divided by the required ___.

output, input

The electrical power is defined by the product of the ___ difference and the ___.

potential, current

In the absence of magnetic, electric, and surface tension effects, the total energy of a system consists of the ___, ____, and ____ energies.

potential, kinetic, internal

The portion of the internal energy of a system associated with the kinetic energies of the molecules (molecular translation, rotation, and vibration, electron and nuclear spin, and electron translation) is called the ___ energy.

sensible

During a process, if the state of the system does not change, the system energy will ___.

stay the same

Heat is a form of energy transfer by virtue of a ___ difference.

temperature

The power transmitted by a shaft is proportional to the ___ and the ___ speed.

torque, rotational

If it is not heat, the energy crossing the boundary of a closed system must be work.

true

Two aluminum spheres with the same mass are located at different elevations. The sphere located at a higher elevation will possess greater potential energy.

true

If a closed system is adiabatic, the only possible energy transfer is...

work

Power is defined by ___ per unit ___.

work, time