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Thermodynamics > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What is a system?

A

A system describe precisely what is being studied

Control mass or control volume

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2
Q

What is the surroundings to a system?

A

Everything external to the system

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3
Q

What is a systems boundary?

A

A boundary distinguishes a system from its boundaries

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4
Q

What is a closed system?

A

A control mass is under study where no mass would cross the boundary

m = constant, Energy can cross the boundary

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5
Q

What is an isolated system?

A

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

No mass & energy would cross any other part of the boundary

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6
Q

What is an open system?

A

A control volume is under study where mass may flow through the boundary

both mass and energy can cross the boundary

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7
Q

Define properties of a system

A

A macroscopic characteristic of a system such as mass, volume, energy, pressure and temperature to which a numerical value can be assigned at a given time without knowledge of the previous behavior (history) of the system

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8
Q

What is an extensive property?

A

A property where its value for an overall system is the sum of its values for the parts into which the system is divided

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9
Q

What is a state of a system?

A

The conditions of system as described by its properties

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10
Q

What is an Intensive Property?

A

Properties that are not additive. Independet of size or extent of a system and may vary from place to place within the system at any moment.

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11
Q

What is steady state?

A

No property change with time

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12
Q

What defines a process

A

A process starts with a property changeing and ends with a change of the state

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13
Q

What is equilibrium?

A

A state of balance where no natural processes can happen

No unbalenced forces in the system

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14
Q

Define Temperature

A

Measures a body´s thermal state.
Measures the state of movement of molecules and atoms. When the movement “ceases” the temperature is the lowest. This is an absolute zero of temperature.

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15
Q

What is the 0th law of thermodynamics?

A

If objects A and B are separately in contact with a third object C, then A and B are in thermal equilibrium with each other if they are both in thermal equilibrium with object C

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16
Q

Define the principle Thermal expansion

Thermometer

A

The volume expansion (or pressure increase) of a (ideal) gas gives the same scale as the thermodynamic temperature scale.

17
Q

What is thermal equilibrium?

A

two objects that have the same temperature are in thermal equilibrium

18
Q

Define the principle Blackbody radiation

Thermometer

A

All objects above absolute zero emit blackbody radiation for which the spectra is directly proportional to the temperature.

19
Q

What is pressure?

A

Pressure is force per unit area, P=F/A
SI pressure units
1 Pa = 1 N/m^2
1 bar = 10^5 Pa = 100 kPa
1 atm = 1.013 bars = 14.7 psi

20
Q

Define Absolute Pressure

A

Pressure with respect to the zero pressure of a complete vacuum.

21
Q

How can you measure pressure?

A

With barometer and manometers the pressure becomes hight of a column of liquid

22
Q

What is Specific Volume?

A

𝑣 =1/𝜌
Unit: m3/kg

23
Q

What is the connection between energy and work?

A

W = ΔEk = ΔEp

24
Q

Sign convention, apply it on work and heat (W, Q).

A

W>0: work done by the system
W<0: work done on the system

Q > 0 heat transfer to the system
Q < 0 heat transfer from the system

25
Q

What is work?

A

Work = force * distance

[J] or [Nm]

26
Q

What is specific work?

A

ε = W/m

27
Q

What is Power?

A

P = dW/dt = ∫ pressure* dVolym

Rate of energy transfer by work

28
Q

What is a Quasiequilibrium process?

A

The process is considered a series of equilibrium states,
i.e. “almost static”
The process is reversible.
The work can be evaluated in terms of changes in system
state

29
Q

What is internal energy U

A

Energy attributed to the motions and configurations of the
individual molecules, atoms, and subatomic particles making up the matter in the system

U [J], u [J/kg]

30
Q

Write an expression for total energy

A

E = Ek + Ep + U

31
Q

What defines energy transfer by heat?

A

Energy exchange between bodies caused by a temperature difference

Q

32
Q

Name 3 types of heat tranfer

A

Conduction
Convection
Radiation

Thermodynamics (8 decks)

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