P1 Flashcards
(111 cards)
1
Q
What is the relationship between energy and work?
A
The energy used equals the amount of work done.
2
Q
What are force and displacement considered in physics?
A
Vectors.
3
Q
What is the formula for work done in terms of force and distance?
A
w = F * s
4
Q
What does gravitational potential energy depend on?
A
mgAh
5
Q
What is the formula for kinetic energy?
A
KE = 1/2 mv^2
6
Q
In what directions does a liquid or gas exert pressure?
A
In all directions.
7
Q
What is the formula for work done by a liquid or gas changing volume?
A
W = p * ΔV
8
Q
What is the unit of pressure?
A
Pascal (Pa)
9
Q
How is pressure measured in terms of force?
A
Newton per square metre (Nm^-2)
10
Q
What is the volume equivalent of 1 cubic metre?
A
1000 litres
11
Q
What does ‘Delta A’ signify in physics?
A
‘Change in’.
12
Q
What is power in terms of energy and work?
A
The rate of using energy or doing work.
13
Q
What is the unit for power?
A
Watt (W) = J/s
14
Q
What is the value of 1 kilowatt in watts?
A
1000 watts
15
Q
What is the value of 1 megawatt in watts?
A
10^6 watts
16
Q
What is the value of 1 gigawatt in watts?
A
10^9 watts
17
Q
What type of energy is associated with chemical bonding?
A
Chemical energy
18
Q
What type of energy is produced during nuclear reactions?
A
Nuclear energy
19
Q
What type of energy is associated with temperature?
A
Thermal energy
20
Q
Calculate the volume of fluid displaced if the diameter of a master cylinder is 10mm and its piston is depressed by 25mm.
A
Use the area of the piston and the depth to calculate.
21
Q
If a slave cylinder piston has a diameter of 50mm, what must be calculated?
A
The pressure of the fluid.
22
Q
What is the relationship between pedal force and braking force in a hydraulic system?
A
The pedal force is transmitted through brake fluid to the slave cylinder.
23
Q
Fill in the blank: The unit for energy is _______.
A
joule (J)
24
Q
What is thermal energy?
A
Energy stored in vibrations, rotations, or random movements of matter
All matter is made up of atoms and molecules. Thermal energy is not visible or measurable.
25
What does the kinetic theory of matter describe for solids?
Atoms having fixed positions but able to vibrate
## Footnote
This theory explains the behavior of solids, liquids, and gases.
26
What characterizes liquids according to the kinetic theory of matter?
Molecules flowing past one another and colliding, while atoms vibrate
## Footnote
The kinetic theory helps understand the behavior of different states of matter.
27
What is the behavior of gases as described by the kinetic theory of matter?
Molecules separated and travelling fast between collisions
## Footnote
Atoms still vibrate and the molecule can spin.
28
How is thermal energy added to materials?
Whenever work is done on them
## Footnote
Examples include stirring, drilling, sawing, hammering, passing electric currents, or pumping fluids.
29
What happens to pastry dough when mixed in a food processor?
It gets warm
## Footnote
Cooling in a fridge is necessary before rolling to prevent it from warming further.
30
What is heat in terms of thermal contact?
The quantity of thermal energy transferred between two bodies
## Footnote
Heat flows from hotter to cooler bodies until thermal equilibrium is reached.
31
What are the three methods of heat transfer?
* Conduction
* Convection
* Radiation
## Footnote
These are the primary ways thermal energy is transferred.
32
What does the Zeroth Law of Thermodynamics state?
There exists a physical quantity called temperature that defines thermal equilibrium between bodies
## Footnote
Two bodies at the same temperature will not exchange heat.
33
What is a thermometer?
Anything with a measurable physical property that varies with temperature
## Footnote
A thermometer must reach thermal equilibrium with its surroundings before reading.
34
What are the two effects of heat transfer into a material?
* Temperature change (sensible heat)
* Change of state (latent heat)
## Footnote
Latent heat refers to energy absorbed or released during a change of state without temperature change.
35
What does latent heat mean?
'Latent' means lying hidden as binding energy of the material
## Footnote
It refers to energy involved in changing states without temperature change.
36
What distinguishes heat from useful work?
Heat transfer is a form of energy that occurs due to temperature differences
## Footnote
Work is energy transferred to perform a task, while heat is energy transferred due to thermal contact.
37
Fill in the blank: A thermometer has to come to _______ with its surroundings before it can be read.
thermal equilibrium
38
What is the ideal gas equation?
pV = NkT
## Footnote
p = pressure, V = volume, N = number of particles, k = Boltzmann's constant, T = temperature
39
What assumptions are made about gas molecules in kinetic theory?
Gas molecules behave like:
* point particles
* elastic collisions
* no significant binding forces between them
40
What is Boltzmann's constant?
1.38 × 10^-23 J/K
41
What does T represent in the ideal gas equation?
T is proportional to the average kinetic energy of the gas molecules
42
What is absolute zero in Kelvin?
0 Kelvin (K)
## Footnote
Absolute zero corresponds to -273.15 °Celsius (°C)
43
What happens to real gases when they are well away from their condensation point?
They behave very like an ideal gas at higher temperatures and lower pressures
44
How should temperature be expressed when using the ideal gas equation?
Always in Kelvin
45
What is the formula to convert Celsius to Kelvin?
T(K) = T(°C) + 273.15
46
What is temperature difference and how can it be expressed?
ΔT = T2 - T1, can be expressed either in Kelvin or Celsius
47
What are some types of practical thermometers?
* Liquid in glass
* Thermistor
* Platinum resistance
* Infrared
* Thermocouple
48
What happens to liquid nitrogen as temperature rises?
Liquid expands
49
What happens to electrical resistance in a thermistor as temperature rises?
Electrical resistance decreases
50
What happens to electrical resistance in a platinum resistance thermometer as temperature rises?
Electrical resistance increases
51
What happens to infrared radiation emitted as temperature rises?
Increase in IR radiation emitted
52
What is the relationship between voltage difference and temperature in a thermocouple?
Voltage difference increases as temperature rises
53
Fill in the blank: Absolute zero is where all thermal energy has been removed and all molecules are in their _______.
ground (lowest possible energy) state
54
True or False: Absolute zero can be practically achieved.
False
55
What is the significance of using absolute temperature in the ideal gas equation?
It ensures valid measurements
56
What is the principle of conservation of energy as it applies to thermal systems?
Q = ΔU + W
## Footnote
This equation states that heat input equals the change in internal energy plus work done by the system.
57
What does Qin represent in energy transfers?
Heat transfers into the system
## Footnote
Qin counts as positive in energy transfers.
58
What does Qout represent in energy transfers?
Heat transfers out of the system
## Footnote
Qout counts as negative in energy transfers.
59
What does work done by the system count as?
Positive
## Footnote
Examples include a hot gas expanding.
60
What is internal energy, U, composed of?
* Thermal energy (heat capacity)
* Chemical and nuclear bond energies
* Energy associated with physical states of matter (latent heat)
* Kinetic or potential energy
## Footnote
Internal energy is complex and cannot be measured in total; we only calculate its changes.
61
How is the change in internal energy calculated?
ΔU = U2 - U1
## Footnote
This formula helps in calculating the change in internal energy of a system.
62
What is the formula for specific heat capacity?
Q = mcΔT
## Footnote
Where Q is heat, m is mass, c is specific heat capacity, and ΔT is the change in temperature.
63
What is the specific heat capacity of water?
c = 4.18 kJkg^-1K^-1
## Footnote
This value indicates the heat required to raise the temperature of 1 kg of water by 1 Kelvin.
64
What is specific latent heat, L?
The heat required to change the physical state of 1 kg of a material
## Footnote
It is calculated using the formula Q = mL.
65
What is the specific latent heat for fusion of ice to water?
L = 333.6 kJkg^-1
## Footnote
This value represents the heat required for melting ice.
66
What is the specific latent heat for vaporization of water to steam?
L = 2.26 MJkg^-1
## Footnote
This value indicates the heat required to convert water into steam.
67
Fill in the blank: Heat transfers, Q, into the system count as _______.
positive
68
Fill in the blank: Work done by the system counts as _______.
positive
69
True or False: Internal energy can be measured directly.
False
## Footnote
Internal energy is too complex to measure in total; only changes are calculated.
70
What is the Second Law of Thermodynamics?
Natural processes are irreversible and cannot be completely reversed.
71
List four examples of natural processes.
* Water flows downhill.
* Heat flows from a hotter body to a colder one.
* Substances mix.
* Gases expand to fill the space available.
72
True or False: Heat will flow from a colder body to a hotter one without an input of work.
False
73
What happens to the entropy of the universe over time?
The entropy is always increasing.
74
Fill in the blank: The reverse of natural processes is _______.
irreversible
75
What is a reversible process?
An idealized process where the system can return to its initial state without any net change.
76
What are the two types of reversible processes?
* Adiabatic
* Isothermal
77
Define adiabatic processes.
Processes with no heat transfer (Q = 0) where work input equals internal energy gained.
78
What occurs when a gas is compressed adiabatically?
A corresponding temperature rise.
79
True or False: Real systems are fully thermally isolated.
False
80
What characterizes isothermal processes?
Two bodies in thermal equilibrium at the same temperature with reversible heat flow.
81
Fill in the blank: In isothermal processes, with zero temperature difference, there would be _______.
no net heat transfer
82
What is necessary for a process to be nearly adiabatic?
Changing things too quickly for heat to be lost.
83
What type of systems can be almost reversible?
Real systems with very small temperature differences, such as heat exchangers.
84
What does the Second Law of Thermodynamics help predict?
The direction of natural change and the position of equilibrium in chemical reactions.
85
What is the main purpose of cycles in engines, refrigerators, and living organisms?
To cause changes and energy transfers to/from their surroundings while the system remains unchanged overall.
86
What does the ideal reversible cycle (Carnot cycle) include?
Two isothermal processes at different temperatures and two adiabatic processes.
87
What is the formula for Carnot efficiency?
Тн - Tc x 100%.
88
In a pressure-volume diagram, what does the area under the p-V curve represent?
The work done for each process.
89
What indicates positive net work done in a cycle on a p-V diagram?
A clockwise direction of the cycle.
90
What type of engines approach the ideal cycle using large heat exchangers?
Power station steam turbines.
91
What do internal combustion engines save by burning fuel inside the cylinder?
The weight of a 'boiler' heat exchanger.
92
What is the benefit of internal combustion engines regarding thermal efficiency?
They benefit from a higher thermal efficiency due to high gas temperature from fuel/air compression followed by combustion.
93
Fill in the blank: The process where heat is added at a constant temperature is called _______.
Isothermal expansion.
94
Fill in the blank: The process where no heat is exchanged with the surroundings is called _______.
Adiabatic.
95
True or False: The efficiency of a heat engine can be determined by the amount of heat transferred in and out.
True.
96
What happens during the change of state on the p-V diagram for water/steam?
A large part of the isothermal lines are also at a constant pressure.
97
What is the role of the exhaust valve in an internal combustion engine?
To release exhaust gases after combustion.
98
What is the function of the fuel injector in an internal combustion engine?
To introduce fuel into the combustion chamber.
99
What is the critical point in the context of steam and water?
The temperature and pressure at which the liquid and vapor phases of a substance become indistinguishable.
100
What is the significance of the critical isotherm?
It represents the temperature at which phase changes occur without a change in pressure.
101
What is the formula for efficiency?
efficiency = 'useful' energy output / total energy input
## Footnote
Efficiency measures how much useful work can be obtained from input energy.
102
What counts as 'wasted' energy in engines?
'Wasted' energy is heat that cannot be converted into 'useful' work
## Footnote
In heating buildings, waste heat can be utilized, making it 'useful'.
103
What is the thermal efficiency formula for a heat engine?
n = (Qin - Qout) / Qin = 1 - (Qout / Qin)
## Footnote
Qin is the heat input and Qout is the waste output heat.
104
What is the significance of TH and Tc in thermal efficiency?
TH is the high temperature of heat input, and Tc is the low temperature of waste heat output
## Footnote
These temperatures are crucial for calculating maximum efficiency.
105
How is maximum efficiency for a Carnot engine expressed?
Nrev = 1 - (Tc / TH)
## Footnote
This formula indicates the theoretical limit of efficiency for reversible engines.
106
How do you convert efficiency from a fraction to a percentage?
Multiply the efficiency fraction by 100%
## Footnote
This conversion is essential for expressing efficiency in a more understandable format.
107
What is a Micro combined heat and power (CHP) system?
A system that can generate electricity while providing heating and hot water
## Footnote
CHP systems enhance energy efficiency by utilizing waste heat.
108
At what temperature does the human body operate as a heat engine?
37°C
## Footnote
The body 'burns' food energy and rejects heat at a lower temperature.
109
What is the rejection temperature of heat from the human body?
Approximately 27°C
## Footnote
This temperature is relevant for calculating the body's efficiency as a heat engine.
110
True or False: No engine can be more thermally efficient than an ideal reversible Carnot cycle engine.
True
## Footnote
The Carnot cycle sets the theoretical maximum efficiency limit for heat engines.
111
Fill in the blank: The waste heat from an engine can become 'useful' heating in a _______.
combined heat and power scheme
## Footnote
This illustrates how waste heat can be repurposed.
