(C1) Thermal Physics in Domestic and Industrial Applications Flashcards

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1
Q

What are prefixes?

A
  • Tera
  • Giga
  • Mega
  • kilo
  • centi
  • milli
  • micro
  • nano
  • pico
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2
Q

Prefix Sizes

A
  • Tera (x10¹²)
  • Giga (x10⁹)
  • Mega (x10⁶)
  • kilo (x10³)
  • centi (x10⁻²)
  • milli (x10⁻³)
  • micro (x10⁻⁶)
  • nano (x10⁻⁹)
  • pico (x10⁻¹²)
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3
Q

What is the law of the conservation of energy?

A

Energy cannot be created or destroyed but can only change form

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4
Q

What are the eight energy stores?

A
  • Magnetic
  • Thermal
  • Chemical
  • Kinetic
  • Electrostatic
  • Elastic Potential (EPE)
  • Gravitational Potential (GPE)
  • Nuclear
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5
Q

What is EPE?

A

Elastic Potential Energy

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6
Q

What is GPE?

A

Gravitational Potential Energy

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7
Q

What is kinetic energy?

A

energy due to an object moving

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8
Q

What is gravitational potential energy?

A

energy due to the position of an object in a gravitational field

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9
Q

What is the equation for gravitational potential energy?

A

GPE = mass x gravitational field x height

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10
Q

What is Earth’s gravitational field strength?

A

9.81

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11
Q

What is thermal energy?

A

energy due to due to the temperature of an object

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12
Q

What is elastic potential energy?

A

Energy due to energy stored when objects are stretched or compressed

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13
Q

What is chemical energy

A

energy that is released by a chemical reactions (fuel and food)

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14
Q

What is nuclear energy?

A

Energy caused by nuclear reactions (radioactivity, fission and fusion)

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15
Q

What is electrostatic energy?

A

Energy from electric charges attracting or repelling

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16
Q

What is magnetic energy?

A

energy from magnets attracting or repelling

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17
Q

Ways of Transferring Energy

A
  • Mechanically
  • Electrically
  • By Heating
  • By Radiation
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18
Q

What is the (Mechanically) way of transferring energy?

A

When a force moves through a distance

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19
Q

What is the (Electrically) way of transferring energy?

A

When a charge moves through a potential difference

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20
Q

What is the (By Heating) way of transferring energy?

A

Due to temperature difference

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21
Q

What is the (By Radiation) way of transferring energy?

A

Due to light, sound, microwaves, etc …

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22
Q

What is work done on a system?

A

Energy is added to the system, the work is negative

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23
Q

What is work done by the system?

A

Energy is leaves the system, the work is positive

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24
Q

What is work done (W) and what is it measured in?

A

When energy is transferred to move an object, measured in joules (J)

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25
Q

What is the equation of work done?

A

W = F × Δs

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26
Q

What is the F in the work done equation and what is it measured in?

A

Force, measured in Newtons (N)

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27
Q

What does the Δ in equations mean?

A

Δ means the change in something

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28
Q

What is the s in the work done equation and what is it measured in?

A

The distance the force has moved, measured in metres (m)

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29
Q

Equation for work done on or by a gas

A

W = p × ΔV

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30
Q

What is the symbol p and what is it measured in?

A

Pressure which is measured in pascals (Pa)

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31
Q

What happens when the temperature of a gas increases at a constant pressure?

A

The volume increases and work is done by the gas (negative)

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32
Q

What happens when the temperature of a gas decreases at a constant pressure?

A

The volume decreases and work is on the gas (positive)

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33
Q

How many kelvins is 0°C?

A

273K

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34
Q

What is power (P)?

A

The rate of doing work, so how fast energy is transferred

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35
Q

Equation of power

A

power = work done / time

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36
Q

What is power measured in?

A

Watts (W)

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37
Q

What is watt equivalent to?

A

One watt is equivalent to one joule per second

38
Q

What is the symbol for time and what is it measured in?

A

t, measured in seconds (s)

39
Q

What is 1 kWh in Joules?

A

3,600,000 J

40
Q

How many units in 1 kWh?

A

One unit

41
Q

What is efficiency?

A

The ratio of the useful energy output of a system to the total input energy

42
Q

Equation for efficiency?

A

Efficiency = useful power output / total power output

43
Q

What is heat transfer?

A

When objects touch, heat energy will be transferred from one to the other

44
Q

What is thermal equilibrium?

A

When touching objects have the same temperature

45
Q

What happens when two touching objects are in thermal equilibrium?

A

There will be no net transfer of heat energy between them

46
Q

What thermal capacity and what is it measured in?

A

The energy required to raise the temperature of a substance by 1°C, measured in J K⁻¹

47
Q

Equation for thermal capacity

A

thermal capacity = Q / ΔT

48
Q

What is the Q in the thermal capacity and specific heat capacity equation?

What is it measured in?

A

(heat energy )
The amount of heat added or removed from the system, measured in joules

49
Q

What is specific heat capacity (c) ?

A

The energy required to raise the temperature of 1kg of a substance by 1°C

50
Q

Equation for specific heat capacity

A

Q=m x c x ΔT

51
Q

What is specific latent heat (L) and what is it measured in?

A

The amount of heat added or removed to change a substance from one state to another

It is measured in J kg⁻¹

52
Q

Equation for specific latent heat

A

Q = m x L

53
Q

What is the specific latent heat of vaporisation of water?
How much energy is needed?

A

The energy need to change water to a vapour
2,260,000 J kg⁻¹

54
Q

What is the latent heat of condensation?

A

When a vapor changes to a liquid

55
Q

What is the specific latent heat of fusion of water?

A

When energy is removed and water turns into ice
336,000 J kg⁻¹

56
Q

What is an ideal gas?

A

A gas that obeys the ideal gas law and its assumptions

57
Q

Ideal gas assumptions

A
  • Particles are in continuous random motion
  • The volume of particles is very small compared to the volume of the gas
  • Particles are a long way from each other and only interact when they collide
  • Collisions are elastic (No kinetic energy is lost during collisions)
58
Q

What is Brownian motion?

A

When fluids are made of particles which hit into things randomly

59
Q

Equation for ideal gas

A

pV = NkT

60
Q

What is N in the ideal gas equation?

A

The number of molecules in the gas

61
Q

What is the k in the ideal gas equation?

A

Boltzmann constant, 1.38 × 10−⁻²³ J K⁻¹

62
Q

What is the first law of thermodynamics?

A

heat energy supplied to a system either increases the temperature, changes the physical state or enables the system to do work

63
Q

Equation of the first law of thermodynamics

A

Q = ΔU + W

64
Q

What is the ​ΔU in the first law of thermodynamics equation?

A

The increase in internal energy

65
Q

What happens if the work is done on the system for the first law of thermodynamics?

A

The first law of thermodynamics equation will become
Q = ΔU − W which will have a negative value

66
Q

What does iso mean?

A

Fixed

67
Q

What is isothermal?

A

Fixed temperature

68
Q

What is isobaric?

A

Fixed pressure

69
Q

What is isovolumetric /isochoric?

A

Fixed volume

70
Q

When does a isothermal change occur?

A

When temperature is constant, ΔU = 0

71
Q

What happens to the first law of thermodynamics during an isothermal change?

A

The first law of thermodynamics equation becomes Q = W

72
Q

During a isothermal change if the gas expands what happens?

A

Work is done and heat must be supplied

73
Q

During a isothermal change if the gas contracts what happens?

A

Heat is produced and must be allowed to leave the gas

74
Q

What does gas need to be isothermally changed?

A
  • It is in a good conducting, thin-walled container​
  • Temperature is constant
  • The change occurs very slowly
75
Q

What is a adiabatic change for ideal gas?

A

When no heat enter or leaves the gas, Q = 0

76
Q

What happens to the first law of thermodynamics during an adiabatic change?

A

The first law of thermodynamics equation becomes ΔU = -W

77
Q

During a adiabatic change if the gas expands what happens?

A

Work is done and the temperature of the gas falls

78
Q

During a adiabatic change if the gas compressed what happens?

A

Work is done and the temperature of the gas rises

79
Q

Is true adiabatic expansion possible?

A

No

80
Q

What is a reversible adiabatic process called?

A

Isentropic

81
Q

What happens in an engine?

A
  1. A piston moves up in a cylinder to compress gas.​
  2. A spark heats the gas.​
  3. The heat causes the gas to expand, moving the piston down.
82
Q

What is the second law of thermodynamics?

A

The transfer or conversion of heat energy is irreversible

83
Q

Equations for the efficiency of a heat engine

A
  1. efficiency = (Q₁ - Q₂) / Q₁
  2. efficiency = W / Q₁
  3. efficiency = 1 - (Q₂ / Q₁)
    all of these are equal to each other, 1=2=3
84
Q

What Q₁ in the heat engine equation?

A

Energy taken from a hot source

85
Q

What Q₂ in the heat engine equation?

A

Energy given to a cold sink

86
Q

Equations for the maximum theoretical efficiency of a heat engine

A

(Q₁ / Q₂) = (T₁ - T₂)

87
Q

What T₁ in the maximum theoretical heat engine equation?

A

Temperature of the source, in kelvin

88
Q

What T₂ in the maximum theoretical heat engine equation?

A

Temperature of the sink, in kelvin

89
Q

What is coefficient of performance (COP)?

A

A ratio of the heat supplied to the high temperature reservoir to work done

90
Q

COP equation

A

COP = T high / (T high - T low)