Energy Flashcards
1
Q
What is a system in physics?
A
An object or group of objects
A system helps narrow down the parameters to focus on relevant observations
2
Q
What happens when a system is in equilibrium?
A
Nothing changes and so nothing happens
3
Q
What is energy measured in?
A
Joules (J)
4
Q
What is an open system?
A
Allows the exchange of energy and matter to or from its surroundings
5
Q
What is a closed system?
A
Can exchange energy but not matter to or from its surroundings
6
Q
What is an isolated system?
A
Does not allow the transfer of matter or energy to or from its surroundings
7
Q
What does the principle of conservation of energy state?
A
Energy cannot be created or destroyed, it can only be transferred from one store to another
8
Q
What is kinetic energy?
A
Energy an object has as a result of its mass and speed
9
Q
What is gravitational potential energy?
A
The energy an object has due to its height in a gravitational field
10
Q
What is elastic potential energy?
A
The energy stored in an elastic object when work is done on the object
11
Q
What is the equation for kinetic energy?
A
Ek = 1/2 m v²
12
Q
What is the gravitational potential energy equation?
A
Ep = m g h
13
Q
What does ‘g’ represent in gravitational potential energy calculations?
A
Gravitational field strength in newtons per kilogram (N/kg)
14
Q
What is the approximate value of gravitational field strength on Earth?
A
9.8 N/kg
15
Q
What energy transfer occurs when a battery powers a torch?
A
Electrical transfer from the chemical store of the battery to the thermal store of the bulb
16
Q
Fill in the blank: Energy is transferred from the hot coffee to the mug to the _______.
A
cold hands
17
Q
What are the energy transfer pathways?
A
- Mechanically
- Electrically
- By heating
- By radiation
18
Q
What happens to energy when a vehicle accelerates?
A
Energy is transferred to the kinetic store of the vehicle
19
Q
What is the formula for calculating elastic potential energy?
A
Ee = 1/2 k e²
20
Q
What is the role of the spring constant (k) in elastic potential energy calculations?
A
It represents the stiffness of the spring in newtons per metre (N/m)
21
Q
What happens to energy when an object falls?
A
Energy is transferred away from its gravitational potential store
22
Q
True or False: Energy can be created or destroyed.
A
False
23
Q
What is the energy transfer when water is boiled in an electric kettle?
A
Electrical working from the mains to the thermal store of the heating element
24
Q
What is the effect of friction on energy transfer when a vehicle slows down?
A
Energy is transferred to the thermal store of the surroundings (dissipated)
25
What is the significance of defining a system in physics?
It helps keep answers concise and focused
26
How is energy transferred when a moving object hits an obstacle?
Energy is transferred to the thermal store of the surroundings and dissipated
27
What are common examples of energy transfers in everyday situations?
* Object projected upwards
* Moving object hitting an obstacle
* Vehicle accelerating or slowing down
* Water boiling in a kettle
28
What should you remember when performing calculations using the kinetic energy equation?
Always double-check that you have squared the speed
29
What is the concept of work done in relation to forces and energy?
Work done is a force acting over a distance and is linked to energy transfer.
30
What are the three energy stores involved when a mass on a vertical spring oscillates?
* Elastic potential energy (EPE) store
* Kinetic energy (KE) store
* Gravitational potential energy (GPE) store
31
At position A of a mass on a spring, what is the energy state of the spring?
* Some energy in elastic potential store (compressed)
* Zero energy in kinetic store (stationary)
* Maximum energy in gravitational potential store (highest point)
32
At position B of a mass on a spring, what is the energy state of the spring?
* Some energy in elastic potential store (stretched)
* Maximum energy in kinetic store (at maximum speed)
* Some energy in gravitational potential store (still above lowest point)
33
At position C of a mass on a spring, what is the energy state of the spring?
* Maximum energy in elastic potential store (maximum extension)
* Zero energy in kinetic store (stationary)
* Minimum energy in gravitational potential store (lowest point)
34
How is gravitational potential energy (EP) calculated?
EP = mgh, where m is mass, g is gravitational field strength, and h is height.
35
What is the maximum change in gravitational potential energy for a student with a mass of 60 kg falling from a height of 75 m?
EP max = 44,100 J
36
How do you calculate the speed of a student after falling 30 m if 90% of the gravitational potential energy is converted to kinetic energy?
v = sqrt(2 * EK / m), where EK = 15,876 J and m = 60 kg.
37
What is the formula for specific heat capacity?
?E = mc??, where ?E is change in energy, m is mass, c is specific heat capacity, and ?? is change in temperature.
38
How is specific heat capacity defined?
The amount of energy required to raise the temperature of 1 kg of a substance by 1 °C.
39
What does a low specific heat capacity indicate about a substance?
It heats up and cools down quickly and takes less energy to change its temperature.
40
What is the aim of the experiment investigating specific heat capacity?
To determine the specific heat capacity of a substance by linking energy transferred to the substance with its rise in temperature.
41
What is the equation for thermal energy supplied to a block in a specific heat capacity experiment?
E = QV and Q = It, combining to E = IVt.
42
What is the significance of systematic errors in a specific heat capacity experiment?
They can cause the measured value of specific heat capacity to be higher than the actual value.
43
What is energy transfer by heating?
Energy transfers by heating increase the energy in the kinetic store of particles, raising the system's temperature or changing its state.
44
What is the impact of work done by forces?
Mechanical work is done when a force acts over a distance, transferring energy between kinetic stores.
45
What is the relationship between current and energy transfer in a circuit?
Energy is transferred electrically from the power supply to the components when a current flows.
46
What happens to energy in an electrical circuit involving a lamp?
* Energy from the chemical store of the cell transfers to the thermal store of the lamp
* Energy is transferred from the lamp to the surroundings by heating and radiation.
47
What is the definition of power in terms of energy transfer?
Power is the rate of energy transfer from one energy store to another over a period of time.
48
What is work done in terms of energy transfer?
Work is done whenever energy is transferred
## Footnote
Electrical work done means energy is transferred when a current flows.
49
How is power defined?
Power is defined as energy transferred per unit time
## Footnote
Power can be calculated using the equation P = E/t.
50
What is the equation for power in terms of work done?
P = W/t
## Footnote
Where P is power in watts, W is work done in joules, and t is time in seconds.
51
What does a power rating indicate?
Power ratings show the amount of energy transferred per unit time.
52
How can you determine which motor is more powerful?
By comparing the time taken to transfer the same amount of energy.
53
What is the unit of power?
The watt (W)
## Footnote
1 W = 1 J/s.
54
Fill in the blank: 1 kilowatt is equal to _______ watts.
1000
55
What does the law of conservation of energy state?
Energy cannot be created or destroyed, it can only be transferred from one store to another.
56
What is useful energy?
Energy that is transferred from store to store and used for an intended purpose.
57
What is wasted energy?
Energy that is not useful for the intended purpose and is dissipated to the surroundings.
58
What happens to energy transfers that are not useful?
They are described as energy being dissipated to the surroundings.
59
What is thermal conduction?
The process where energy is transferred by vibrating particles in a substance.
60
What is an insulator?
A substance that is a poor thermal conductor.
61
List three examples of substances with high thermal conductivity.
* Diamond
* Aluminium
* Graphite
62
List three examples of substances with low thermal conductivity.
* Air
* Steel
* Bronze
63
What factors affect conduction?
* Temperature difference across the material
* Thickness of the material
* Thermal conductivity of the material
64
How can wasted energy in mechanical processes be reduced?
By reducing friction through lubrication.
65
What does insulation do in a home?
Lowers the rate of cooling, meaning less energy is lost to the outside.
66
What is the effect of thickness on energy transfer through insulation?
The thicker the material, the less energy will be transferred by conduction.
67
How can you calculate power using energy and time?
Using the equation P = E/t.
68
What is the relationship between power and time for two cars transferring the same energy?
The car with more power will transfer energy in a shorter amount of time.
69
When lifting the same weight, how can two motors differ in power?
One motor can lift the weight faster than the other.
70
What is the relationship between power and energy transfer?
Power describes how fast the energy is transferred from one store to another.
71
What causes energy dissipation to thermal stores?
Heating, light, and sound during energy transfers.
72
What is the effect of friction on energy transfers?
It transfers energy from the kinetic store by heating to the objects and surroundings.
73
What does the temperature difference affect in terms of conduction?
The greater the temperature difference, the more conduction occurs.
74
What is the purpose of cavity wall insulation?
To lower the conduction of heat through the walls from the inside to the outside.
75
What is the effect of several layers of insulation on cooling?
It decreases the rate of cooling.
76
How does insulation in walls affect heat loss from a building?
Less heat is lost from a building.
77
What material is commonly used for cavity wall insulation in cold countries?
Blown mineral fibre filled with gas.
78
What is the aim of the practical experiment investigating insulation?
To investigate the effectiveness of different materials as thermal insulators.
79
What is the independent variable in the insulation experiment?
Type of material.
80
What is the dependent variable in the insulation experiment?
Temperature, T (°C).
81
List three control variables in the insulation experiment.
* Volume of water
* Starting temperature of the water
* Thickness of each material.
82
What is the resolution of the thermometer used in the experiment?
1 °C.
83
What is the method step involving the thermometer in the insulation experiment?
Place the thermometer through a hole in the cardboard lid into the water.
84
How often should the temperature be recorded during the insulation experiment?
Every 2 minutes for 20 minutes.
85
What does a graph of temperature against time in the experiment show?
The temperature falls quickly at high temperatures, then more slowly.
86
What does a shallow curve on the temperature graph indicate?
That material is the best insulator.
87
What is a systematic error to consider in the insulation experiment?
Starting temperature of the water should be the same for each material.
88
What is one alternative method to improve the insulation experiment?
Using one material with different thicknesses.
89
What is the definition of efficiency in a system?
A measure of the amount of wasted energy in an energy transfer.
90
How is efficiency defined mathematically?
Efficiency = useful output energy transfer / total input energy transfer.
91
If a system has low efficiency, what does it imply?
Most of the energy transferred is wasted.
92
What is the efficiency of an electric motor that lifts a load with an output power of 117.6 W?
35%.
93
What is one way to improve the efficiency of a device?
Reducing wasted energy transfers.
94
What are two causes of wasted energy in machines?
* Friction
* Air resistance.
95
How can friction be reduced in mechanical systems?
By adding bearings or lubricating parts.
96
What is one method to reduce electrical resistance in circuits?
Using components with lower resistance.
97
How can air resistance be minimized for moving objects?
By streamlining their shapes.
98
What is a common method to reduce noise from machinery?
Tightening loose parts.
99
What are energy resources?
Large stores of energy that can be used to generate electricity and heat homes and businesses.
100
How is electricity generated regardless of the energy resource used?
A turbine is turned, which turns a generator, generating electricity.
101
What is the role of water in hydroelectric power generation?
Water turns turbines in hydroelectric dams, tidal barrages, and tidal turbines.
102
What type of energy transfer occurs in a hydroelectric dam?
Gravitational potential energy of water is converted to kinetic energy of the turbine.
103
How do fossil fuels generate electricity?
They are combusted to heat water, producing steam to turn turbines.
104
What are the energy transfers involved in electricity generation from fossil fuels?
Chemical store of fuel → thermal store of water → kinetic store of turbine → kinetic store of generator.
105
What is the process of electricity generation in a nuclear power plant?
Nuclear store of fuel → thermal store of water → kinetic store of turbine → kinetic store of generator.
106
What is geothermal energy used for?
To produce steam that turns turbines by pumping water down to hot rocks.
107
Define renewable energy resources.
Energy sources that are replenished at a faster rate than the rate at which they are being used.
108
List examples of renewable energy resources.
* Solar energy
* Wind
* Bio-fuel
* Hydroelectricity
* Geothermal
* Tidal
109
What are non-renewable energy resources?
Energy sources that cannot be replenished quickly, including fossil fuels and nuclear fuel.
110
What are the three main uses of energy resources?
* Transport
* Electricity generation
* Heating
111
What type of energy resources power most vehicles?
Petroleum products such as petrol, diesel, and kerosene.
112
What is the advantage of electric vehicles?
They produce zero carbon emissions while being driven.
113
What is the disadvantage of charging electric vehicles?
They are connected to the National Grid, which uses a mix of renewable and non-renewable sources.
114
True or False: Biofuels are considered carbon-neutral.
False. The claim that biofuels are carbon-neutral is controversial.
115
What percentage of the world's energy is produced by non-renewable sources?
84%.
116
What is the main disadvantage of using natural gas for heating?
It is a non-renewable energy resource.
117
What is the definition of a reliable energy resource?
An energy resource that can produce energy at any time.
118
What is a non-reliable energy resource?
Resources that can only produce energy some of the time, such as wind energy.
119
What are the main challenges currently faced by fusion energy?
* Achieving high temperatures
* Maintaining high pressures
* Containing the fusion process
120
What is the Greenhouse Effect?
The process where greenhouse gases trap infrared radiation, leading to global warming.
121
List some consequences of global warming.
* Climate change
* Rising sea levels
* Extinction of species
* Migration of species
* Spread of diseases
* Loss of habitat
122
What has happened to fossil fuel use in the UK in the past 30 years?
Dropped from 75% to 38%.
123
What has happened to renewable energy use in the UK in the past 30 years?
Increased from 2% to 35%.
124
What is one of the main reasons for switching from coal to natural gas?
Coal produces the most carbon dioxide among fossil fuels, while natural gas produces the least.
125
What is required to further reduce carbon emissions?
* More nuclear power stations
* Energy storage solutions for unreliable sources
