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MED 101- PHYSICS I > 11. THERMODYNAMICS > Flashcards

11. THERMODYNAMICS Flashcards

1
Q
  1. What do all activities of the human body involve?
A
  • energy consumption
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2
Q
  1. What is metabolism?
A
  • the processes of the body that involve:
    - energy intake
    - storage
    - use of energy
  • it is any energy usage by the body
  • it is also the sum of all the chemical processes performed by the cells
  • they do this is in order to keep the body alive
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3
Q
  1. What is the body, from a physics perspective?
A
  • it is an energy converter
  • this means that it is subject to the law of conservation of energy
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4
Q
  1. What 4 functions does the body do with the energy that it takes in from food?
A
  • it operates its organs
  • it maintains a constant temperature
  • it does external work
  • it builds a stored energy supply (fat) for later needs
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5
Q
  1. What is thermodynamics?
A
  • it is the study and application of the thermal energy of systems
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6
Q
  1. What is a central topic of Thermodynamics?
A
  • temperature
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7
Q
  1. What is temperature?
A
  • it is a measure of how hot or cold something is
  • it is how we measure heat
  • it is one of the seven SI base quantities
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8
Q
  1. What is temperature usually measured in?
A
  • Celsius
  • Fahrenheit
  • Kelvin Scale
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9
Q
  1. What is the SI unit for temperature?
A
  • Kelvins (K)
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10
Q
  1. What limits does the temperature of the body have?
A
  • it has no upper limits
  • it has a lower limit
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11
Q
  1. What is the lower limit of body temperature?
A
  • the limiting low temperature is taken as the zero of the Kelvin Temperature scale
  • this is equal to -273.15 °C
  • this is equal to -459.67 °F
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12
Q
  1. What equation do we use to move from Celsius to Fahrenheit?
A

T (F°) = T (C°) x 9/5 + 32

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13
Q
  1. What equation do we use to move from Kelvin to Celsius?
A

T (C°) = T (K) - 273.15

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14
Q
  1. What is Heat (▵Q)?
A
  • it is the thermal energy that flows from one body or system to another
  • the two systems are in contact with each other
  • it flows from one system to another due to their temperature differences
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15
Q
  1. How does heat always flow?
A
  • from hot to cold
  • the movement of thermal energy is always from hot to cold
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16
Q
  1. What is the SI unit for Heat?
A
  • Joules (J)
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17
Q
  1. What are two other units for heat?
A
  • calories
    (1 cal= 4.184 J)
  • British thermal unit
    (1 Btu= 1054 J)
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18
Q
  1. What does it mean when two systems are in equilibrium?
A
  • they are balanced
  • they share a property (temperature)
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19
Q
  1. What is thermal equilibrium?
A
  • it is when two systems are in thermal contact:
    • they exchange energy until an equilibrium state is
      reached
    • then no more net energy transfer occurs
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20
Q
  1. What does the zeroth law of thermodynamics state?
A
  • If Bodies A and B are in thermal equilibrium with a third body C
  • then body A and B are in thermal equilibrium with each other
21
Q
  1. What is the message of the zeroth law?
A
  • every body has a property called temperature
  • when two bodies are in thermal equilibrium:
    - their temperatures are equal and vice versa
22
Q
  1. How can the conservation of the energy in the body be written?
A

Change in the stored energy in the body
=
Heat lost from the body + the work done

23
Q
  1. What do we use the first law of thermodynamics to investigate?
A
  • the continuous energy changes in the body
24
Q
  1. What is the First Law of Thermodynamics?
A
  • The First Law of Thermodynamics states that energy cannot be created or destroyed; it can only be converted from one form to another.
25
Q
  1. What is the equation for the first law of Thermodynamics?
A

▵U = Q - W

▵U= the change in the internal energy

Q= the heat added to the system

W= the work done by the system

26
Q
  1. What change does an object experience when it changes its temperature?
A
  • it changes size
  • there is a change in any linear dimension (▵L)
    when there is a change in temperature (▵T)
27
Q
  1. What is the equation we use to find the change in any linear dimension/ size of the object?
A

▵L = L . ⍺ . ▵T

⍺= the coefficient of linear expansion

28
Q
  1. What is the equation we use to find out the change in volume (▵V) in a solid or a liquid?
A

▵V = V . β . ▵T

β= the coefficient of volume expansion
= 3⍺

29
Q
  1. What is the specific heat capacity (c)?
A
  • it is the quantity of heat that is required to change the temperature of unit mass
    of a substance
    by one degree
30
Q
  1. What equation will we use to work out the specific heat capacity?
A

c = ▵Q / m . ▵T

c= specific heat capacity

▵Q= quantity of heat

m = mass

▵T= temperature change

31
Q
  1. What is the SI unit of the specific heat capacity (c)?
A
  • J/kg.K
  • other units also include:
    - kcal
    - kg. °C
32
Q
  1. What does each substance have?
A
  • it has a characteristic value of specific heat
  • this varies slightly with temperature
33
Q
  1. What is the characteristic value of specific heat for water?
A
  • c water = 1 kcal/kg.°C
    = 4180 K/kg.°C
  • this value changes dependent on the phase water is found in
    (liquid, solid, vapour)
34
Q
  1. What is the average specific heat for the human body
A
  • c body = 0.83 kcal/kg.°C
  • this means that it takes 83kcal to raise the temperature of a 100kg person by 1°C
35
Q
  1. What does Thermal Conductivity (K) describe?
A
  • it describes how temperature varies spatially
  • this is due to the heat flow between different regions
  • these regions are separated by a distance (▵x)
  • it also describes how much heat flows due to the spatial variation in temperature
36
Q
  1. How would we mathematically write the relation between heat flow and spatial variation in temperature?
A

1 dQ ▵T
—– x ——– ≈ -K ————
A dt ▵x

  • this is known as heat flux
  • the minus sign indicates that the heat flows from hotter regions to colder regions
37
Q
  1. What is a consequence of thermal dynamics?
A
  • heat engines that convert chemical energy to heat
  • and that use heat for mechanical work
  • have a limited efficiency to do such useful mechanical work
38
Q
  1. What does the efficiency of a heat engine describe?
A
  • how efficiently it turns heat to work
  • how well-organised it is
  • how much max productivity it can do with minimum waste
39
Q
  1. How do we work out the efficiency ?
A

Work Done
n = —————————-
Energy Consumed

40
Q
  1. What is the % of human efficiency?
A
  • 5.8%
41
Q
  1. What value does efficiency rarely exceed?
A
  • 20%
42
Q
  1. What does the first law of thermodynamics show?
A
  • it shows that stored energy can be used to supply heat or work
  • this is known as mechanical work with regards to people
43
Q
  1. What is the mechanical work?
A

the force you apply to an object
x
the distance you push or pull it by

44
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes
45
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes
46
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes
47
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes
48
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes
49
Q
  1. Read through this summary.
    Does everything make sense
A
  • yes

MED 101- PHYSICS I (28 decks)

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