test 1.1 Flashcards by Robert Bohn

Systems can be studied only from a macroscopic point of
view.

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A control volume is a special type of closed system that
does not interact in any way with its surroundings.

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Only changes in the internal energy of a system between
two states have significance: No significance can be attached
to the internal energy at a state.

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A system is said to be at ____________ if none of its
properties changes with time.

steady state

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In order to evaluate work using W (integral)V2 V1
pdV , we must
specify how p varies with V during the process. It follows
that work is not a

property, because it is a process

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A special type of closed system that does not interact in
any way with its surroundings is an

isolated system

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During a quasiequilibrium process, the departure of the state
of the system from thermodynamic equilibrium is at most
infinitesimal. How accurate is this model for a real expansion?

not accurate

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A rotating flywheel stores energy in the form of kinetic
energy.

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Body organs, such as the human heart, whose shapes
change as they perform their normal functions can be
studied as control volumes.

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The Rankine degree is a smaller temperature unit than the
Kelvin degree.

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Kinetic and gravitational potential energies are extensive
properties of a closed system. Explain.

extensive, depends on mass

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According to Archimedes’ principle, the magnitude of the
buoyant force acting on a submerged body is equal to the
weight of the body.

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For heat pumps, the coefficient of performance gamma is always
greater than or equal to one.

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Intensive properties may be functions of both position and
time, whereas extensive properties can vary only with time.

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The value of a temperature expressed using the Rankine
scale is always higher than its value expressed using the
Fahrenheit temperature scale.

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Temperature is an extensive property.

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In principle, expansion or compression work can be
evaluated using (integral) p dV for both actual and quasiequilibrium
expansion processes.

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A control volume is a system that

(a) always contains the same matter.
(b) allows a transfer of matter across its boundary.
(c) does not interact in any way with its surroundings.
(d) always has a constant volume.

(b) allows a transfer of matter across its boundary.

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Power is related mathematically to the amount of energy
transfer by work by integrating over time.

P = W/t

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A dielectric material in a uniform electric field can
experience energy transfer by work if its polarization
changes.

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When a system undergoes a process, the terms work and
heat do not refer to what is being transferred. _______ is
transferred when work and/or heat transfer occurs.

energy

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Gage pressure indicates the difference between the absolute
pressure of a system and the absolute pressure of the
atmosphere existing outside the measuring device

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The symbol D is always used to denote

(a) initial value minus final value
(b) no change in value
(c) final value minus initial value
(d) none of the above

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The energy of an isolated system can only increase.

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Current passes through an electrical resistor inside a tank of gas. Depending on where the system boundary is located, the energy transfer can be considered work or heat.

Define a polytropic process.

pvⁿ= constant

Explain why the value for gage pressure is always less than the corresponding value for absolute pressure.

local atmospheric pressure

The rate of heat transfer at steady state by conduction through a plane wall is greater if the wall is fabricated from plywood than from concrete, assuming the same wall area and temperature gradient.

The composition of a closed system cannot change.

The kilogram for mass and the meter for length are examples of SI base units defined relative to fabricated objects.

A closed system always contains the same matter; there is no transfer of matter across its boundary.

Temperature is the property that is the same for each of two systems when they are in thermal equilibrium.

What are the three modes of energy storage for individual atoms and molecules making up the matter within a system?

translation vibration rotation

For any cycle, the net amounts of energy transfer by heat and work are equal.

If a closed system undergoes a process for which the work is negative and the heat transfer is positive, the total energy of the system must increase.

T E = Q - W

If a system’s temperature increases, it must have experienced heat transfer.

F, stirring

In local surroundings at standard atmospheric pressure, a gage will indicate a pressure of 0.2 atm for a refrigerant whose absolute pressure is 1.2 atm.

Volume is an extensive property.

Mass is an intensive property.

The value of the temperature expressed using the Celsius temperature scale is always higher than its value expressed using the Kelvin scale.

If the value of any property of a system changes with time, that system cannot be at steady state.

A spring is compressed adiabatically. Its internal energy increases.

What is the thermodynamic definition of work?

work is done on a system when the only effect on everything external to the system is expressed in terms of raising a wieght

The pressure unit psia indicates an absolute pressure expressed in pounds force per square inch.

Devices that measure pressure include barometers, Bourdon tube gages, and manometers.

A system is at steady state if (a) none of its properties changes with time. (b) none of its properties changes with location within the system. (c) none of its properties changes with time or with location within the system. (d) none of the above.

(a) none of its properties changes with time.

Specific volume, the volume per unit of mass, is an intensive property whereas volume and mass are extensive properties.

When a closed system undergoes a process between two specified states, the change in temperature between the end states is independent of details of the process.

Pressure is an intensive property.

Both the Kelvin scale and the Rankine scale are absolute temperature scales.

Thermal radiation can occur in vacuum.

The total energy of a closed system can change as a result of energy transfer across the system boundary by heat and work and energy transfer accompanying mass flow across the boundary.

F, not mass

The statement, “When two objects are in thermal equilibrium with a third object, they are in thermal equilibrium with each other,” is called the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.

zeoth law

The differential of work, W, is said to be an \_\_\_\_\_\_\_\_\_ differential.

in exact, need process details

Work is not a property.

T inexact differentials

The resultant pressure force acting on a body completely or partially submerged in a liquid is the \_\_\_\_\_\_\_\_\_\_\_\_.

buoyancy force

The pound force, lbf, is equal to the pound mass, lb.

Based on the mechanisms of heat transfer, list three reasons why energy transfer by heat may be negligible.

temp diff good insulator small surface area

The heat transfer coefficient, h, in Newton’s law of cooling is not a thermodynamic property. It is an empirical parameter that incorporates into the heat transfer relationship the nature of the flow pattern near the surface, the fluid properties, and the geometry.

If a system is isolated from its surroundings and no changes occur in its observable properties, the system was in equilibrium at the moment it was isolated.

SI base units include (a) kilogram (kg), meter (m), newton (N). (b) kelvin (K), meter (m), second (s). (c) second (s), meter (m) pound mass. (d) kelvin (K), newton (N), second (s).

(b) kelvin (K), meter (m), second (s).

The change in total energy of a closed system other than changes in kinetic and gravitational potential energy are accounted for by the change in \_\_\_\_\_\_\_\_.

internal energy

One nanosecond equals 10⁹ seconds.

The change in gravitational potential energy of a 2-lb mass whose elevation decreases by 40 ft where g = 32.2 ft/s2 is 22576 ft ? lbf.

F lbf conversion

According to the Stefan–Boltzmann law, all objects emit thermal radiation at temperatures higher than 0 K (0 R).

vessel holding 0.5 kg of oxygen (O2) contains 16 lb of O2.

Kilogram, second, foot, and newton are all examples of SI units.

Cooling of computer components achieved by a fan-induced air flow falls within the realm of radiation heat transfer.

The specific volume is the reciprocal of the density.

1 N equals 1 kg m/s² but 1 lbf does not equal 1 lb ft/s².

An object of known mass and initially at rest falls from a specified elevation. It hits the ground and comes to rest at zero elevation. Is energy conserved in this process? Discuss.

yes, PE to KE

What direction is the net energy transfer by work for a refrigeration or heat pump cycle: in or out? The net energy transfer by heat?

in and out W cycle = Q out - Q in and W cycle is always positive so Qout needs to be positive

When a system is isolated, (a) its mass remains constant. (b) its temperature may change. (c) its pressure may change. (d) all of the above.

(d) all of the above.

In mechanics, the work of a resultant force acting on a body equals the change in its \_\_\_\_\_\_\_\_\_.

kinetic energy

\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is pressure with respect to the zero pressure of a complete vacuum.

absolute pressure

The volume of a closed system can change.

For a system at steady state, no property values change with time.

If a closed system undergoes a thermodynamic cycle, there can be no net work or heat transfer.

What is the objective of an engineering model in thermodynamic analysis?

model problem, simplify assumptions, listing ideas

If a closed system undergoes a process for which the change in total energy is positive, the heat transfer must be positive.

The list consisting only of intensive properties is (a) volume, temperature, pressure. (b) specific volume, mass, volume. (c) pressure, temperature, specific volume. (d) mass, temperature, pressure.

A process that is adiabatic cannot involve work.

What direction is the net energy transfer by work for a power cycle: in or out? The net energy transfer by heat?

out and in power cylce does work on its surroundings, needs heat input

test 1.1 Flashcards

(83 cards)