P1 Flashcards
How does the temperature of an object affect the amount of infrared radiation it emits?
The hotter the object, the more infrared radiation it emits
How do we know infrared radiation can pass through a vacuum?
Earth receives energy from the sun. In order for this energy to reach earth it must pass through space; which is a vacuum, thus proving infrared can indeed pass through a vacuum.
What colour is the best emitter of infrared radiation?
Matt Black
What colour is the best reflector of Infrared Radiation?
Light, shiny surfaces
What are the properties used to describe each state of matter?
Flow, Shape, volume and Density
Describe the arrangement of particles in a solid
The particles in a solid are held next to each other, vibrating in their fixed positions.
Describe the arrangement of particles in a Liquid
The particles in a liquid move about at random and are in contact with each other.
Describe the arrangement of particles in a Gas
The particles in a gas move about randomly and are much farther apart than particles in a solid or liquid.
In which state of matter does conduction occur?
Solid
How does conduction occur?
If one end of a solid is heated, the particles at that end gain kinetic energy and and vibrate more. This energy is then passed to neighbouring particles and in this way the energy is transferred through the solid.
What makes metals such good conductors?
The delocalised electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles.
Why is trapped air a good insulator?
trapped air cannot conduct electricity as it is not a solid, thus it makes for a good insulator.
In which state of matter does convection occur?
Fluids
Explain how convection occur
When a fluid is heated it gains thermal energy and it expands. The fluid becomes less dense and rises. The warm fluid is replaced by cooler, denser fluid. The resulting convection current transfers energy throughout the fluid.
Give an example of a large scale convection current
Wind (Onshore/Offshore breezes)
Why does evaporation cause a cooling effect?
The most energetic liquid molecules escape from the liquid’s surface and enter the air. Therefore, the average kinetic energy (Particle movement is what heat is) of the remaining molecules is less, so the temperature of the liquid decreases.
How can the rate of evaporation be increased?
- ) Increasing the surface area of the liquid
- ) Increasing the temperature of the liquid
- ) Creating a draught of air across the liquid’s surface
How can the rate of condensation be increased?
- ) Increasing the surface area
2. ) Reducing the surface temperature
What is the term for when a substance turns straight from a solid to gas?
subliming
What factors can affect the rate of energy transfer?
- ) Temperature Difference (Higher=faster rate)
- )The material the object is in contact with
- ) The object’s shape
- ) The object’s surface area
Define Specific Heat Capacity
The amount of energy needed to raise the temperature of 1Kg of the substance by 1c.
Unit J/Kg^0c
Would a piece of 2kg copper need more or less energy than a 1Kg piece in order to raise the temperature by 1C
Yes a piece of copper that weighs 2Kg will require 2x as much energy in order to become 1C warmer.
What is the equation for specific heat capacity?
E=mc0 Where: E = energy transferred (J) m= mass (Kg) c= specific heat capacity (J/KgC) 0= Theta, temperature change (C)
What techniques are used to minimise the rate of energy transfer out of homes ?
Fibreglass loft insulation Cavity wall insulation Double Glazing Draught Proofing Aluminium Foil behind radiators
How does Fibreglass loft insulation help reduce heat transfer?
The insulation is a very good thermal insulator, and prevents heat transfer via conduction
How does cavity wall insulation work?
Cavity wall insulation traps air in small pockets to reduce energy transfer via convection, as currents can no longer form
How does double glazing help reduce heat transfer?
Double glazing means there is a layer of air between each pane. Since conduction can only occur in solids, the air space between the panes means heat cannot be transferred via conduction.
How does draught proofing prevent heat loss ?
Draught excluders prevent air from the outside entering the house. As the temperature differential would be quite large a convection current would be former thus heat lost
How does placing aluminium foil behind radiators reduce heat loss?
The foil reflects the heat back into the centre of the room meaning no heat is wasted on hearing walls.
What is the U-value of a material
The U-value of a material is how much energy passes/m^2 for 1C temperature difference.
What are solar heating panels and what are the advantages and disadvantages?
Solar panels contain water that is heated by radiation from the sun. This water may then be used to heat buildings or provide domestic hot water.
Pros: solar panels are cheap to run as they don’t use fuel, furthermore this makes them eco-friendly.
Cons: They are expensive to buy and install and the water isn’t heated at night.
What are the types of energy?
MostKidsHateLearningGCSEEnergyNAMES Magnetic kinetic heat light gravitational chemical sound elastic electrical nuclear
Although energy cannot be created or destroyed, it can be?
Transformed
Define a machine
A machine is something that transfers energy from either:
A.) One place to another
B.) One form to another.
A machine outputs two types of energy, these are:
Useful Energy
Wasted Energy
The most common form of wasted energy is?
Heat Energy, caused by friction between the moving parts of the machine.
what is the unit for energy?
joules (J)
Define efficiency
How much of the output energy is useful.
What is the equation for efficiency?
Useful energy transferred by appliance
Energy= ————————————————————–
Total energy supplied to appliance
How can energy transfer through an appliance be represented?
Using a Sankey Diagram
It is very rare to have an appliance with 100% efficiency, provide and example of an appliance that is generally considered 100% efficient.
Electric Heater
What is the power of an appliance?
The rate at which it transfers energy
What is the unit for energy power?
watt (W)
How many joules of energy does a 1 watt appliance transfer per second?
1 J, 1 watt= 1J/s
Often a watt is too small of a measurement in which case killowatt (kW) can be used, How many watts is a kilowatt?
1000
What is the equation for energy power?
E
P= ---------
t
Where:
P: Power (W)
E: Energy (J)
t: Time taken for energy to be transferred (s)Define kilowatt-hour (kWh)
The energy supplied to a 1kW appliance in one hour.
What is the equation for the amount of energy transferred to a mains appliance?
E=Pt
Where:
E is the energy transferred in killowatt-hours, (kWh)
P is the power of the appliance (kW)
t is the time taken (in hours) for the energy to be transferred
What is a electricity meter?
A device which records the number of kWh consumed.
What is the equation for total energy cost?
Total Cost= number of kWh x cost per kWh
What factors must be considered when comparing the cost effectiveness of different appliances?
- the cost of buying the appliance
- the cost of installing the appliance
- the running cots
- maintenance costs
- environmental costs
- loan interest (if a loan is required to purchase the appliance).
Define ‘Payback Time’
The time it takes for an appliance or installation to pay for itself in terms of energy savings.
Describe how electrical energy is produced in a power station
- Fossil fuel is burned in order to heat water.
- The water boils, forming steam.
- This steam drives a turbine which is coupled to an electrical generator.
How does the process change in some gas-fired power stations?
Hot gases directly drive the turbine rather than any water being heated.
What is a ‘Biofuel’
A biofuel is any fuel obtained from living or recently living organisms. Some biofuels can be used in small-scale, gas fired power stations. Biofuels are a renewable source of energy.
What fuels are usually used in nuclear power stations?
Usually, uranium is used. However, plutonium is also sometimes used.
How do nuclear power stations work, and why do they produce so much energy?
- The nucleus of a Uranium atom can undergo a process called Nuclear Fission. This process releases energy.
- There are lots of Uranium nuclei, so lots of fission reactions take place, releasing lots of energy. This energy is used to heat water, turning it into steam.
Name the three main sources of renewable energy
Wind
Waves
Tidal
How can energy be obtained from wind?
The energy from the wind directly drives a turbine.
In a wind turbine, the wind passing over the blades makes them rotate and drive a generator at the top of a narrow tower.
How can energy be obtained from water?
Energy can be obtained from ;
- Falling Water
- Waves
- Tides
What is Hydroelectric Power?
Water is collected in a reservoir. This water is allowed to flow downhill and turn turbines at the bottom of the hill.
What is a pumped storage system?
At times of low energy demand, surplus electricity is used to pump water back up the hill to the top of the reservoir. This means that the energy is stored. Then at times of high demand the water can be released to fall through the turbines and transfer the stored energy to electrical energy.
What is wave power?
We can use the movement of waves on the sea to generate electricity. The movement drives a floating turbine that turns a generator. Then the electricity is delivered to the grid system on shore by cable.
What is tidal power?
The level of the sea around the coastline rises and falls twice each day. These changes are called tides. If a barrage is built across a river estuary, the water at each high tide can be trapped behind it. When the water is released to fall down to the lower sea level, it drives turbines.
What is a solar cell?
Solar energy travels from the sun through space as electromagnetic radiation. A solar cell can transfer this energy into electrical energy.
What is a solar heating panel?
A solar heating panel works on the same concept as a solar cell. However, instead of converting the infrared energy into electrical energy, it is simply used to heat water.
What is a solar power tower?
A solar power tower uses thousands of mirrors to reflect sunlight onto a water tank to heat the water and produce steam.
What is geothermal energy?
Geothermal energy is produced inside the earth by radioactive processes and this heats the surrounding rock. In volcanic or other suitable areas, very deep holes are drilled and cold water is pumped down to the hot rocks. There it is heated and comes back to the surface as steam. The steam is used to drive turbines etc.
Define a non-renewable energy resource
A non renewable resource is a resource which is used much faster than it replenishes, causing reserves to diminish.
Define a renewable energy resource
A resource which can be produced as fast as they are used.
Give the advantages and disadvantages of using COAL as a resource.
ADVANTAGES
Bigger reserves than other fossil fuels
Reliable
DISADVANTAGES
Non-renewable
Production of CO2, a green house gas
Production of SO2, causing acid rain
Give the advantages and disadvantages of using OIL as a resource.
ADVANTAGES
Reliable
DISADVANTAGES
Non-renewable
Production of CO2, a green house gas
Production of SO2, causing acid rain
Give the advantages and disadvantages of using GAS as a resource.
ADVANTAGES
Reliable
DISADVANTAGES
Non-renewable
Production of CO2, a green house gas
Give the advantages and disadvantages of using NUCLEAR as a resource.
ADVANTAGES
No production of polluting gases.
Reliable
DISADVANTAGES
Non-renewable
Produces hazardous nuclear waste, which is difficult to dispose of safely
Small risk of a big nuclear accident.
Give the advantages and disadvantages of using WIND as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
DISADVANTAGES
Requires many large turbines
Not reliable, as the wind doesn’t always blow.
Give the advantages and disadvantages of using FALLING WATER as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
Reliable in wet areas
DISADVANTAGES
Only works in wet areas
Damming the areas causes flooding and affects the local ecology.
Give the advantages and disadvantages of using WAVES as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
DISADVANTAGES
Can be a hazard to boats
Not reliable
Give the advantages and disadvantages of using TIDES as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
Reliable always tides twice a day
DISADVANTAGES
Only a few river estuaries are suitable
Building a barrage affects local economy
Give the advantages and disadvantages of using SOLAR as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
Reliable in hot countries in the day time
DISADVANTAGES
Only produce a small amount of electricity
Unreliable in less sunny countries
Give the advantages and disadvantages of using GEOTHERMAL as a resource.
ADVANTAGES
No production of polluting gases
Renewable
Free energy resource
DISADVANTAGES
Only economically viable in a very few places.
Drilling through large depth of rock is difficult and expensive.
What is the National Grid?
A network of pylons, cables and transformers
What is the national grid voltage?
132 000 V or more
At what voltage is the electricity produced by power stations?
25 000 V
What is the voltage of home and office electricity?
230V
How is the voltage increased from 25 000V to 132 000 V
using a step up transformer
Why is the electricity sent through the grid at such a high voltage?
Transmission at high voltage reduces the energy wasted in cables, making the system more efficient.
What sources of energy are used to meet ‘base load’ demand?
Nuclear
Coal
Oil
What sources of energy are used to meet ‘variable’ demand?
Gas Fired
Pumped Storage Schemes
Other renewable sources
What are the energy sources for electricity ? (and percentage)
Gas-46% Coal-41% Nuclear-16% Oil-1% Hydro-1% Other fuels and renewable sources-5%
Which source has the fastest ‘start up time’ ?
Gas-fired stations
Which source has the slowest ‘start up time’?
Nuclear
What are waves used for ?
To transfer energy and information
In which direction to waves transfer energy?
In the direction of travel of the waves
What are the types of wave?
Transverse
Longitudinal
Describe the oscillation pattern of a transverse wave
For a transverse wave the oscillation (vibration) of the particles is perpendicular to the direction in which the waves travel.
Describe the oscillation pattern of a longitudinal wave
For a longitudinal wave the oscillation of the particles is parallel to the direction of travel of the wave.
What is a longitudinal wave made up of?
A longitudinal wave is made up of compressions and rarefactions .
What are EMR waves?
E.G. light waves and radio waves, can travel through a vacuum. There are no particles moving in an electromagnetic wave, as these waves are oscillations in electric and magnetic fields. The oscillations are perpendicular to the direction of travel of the wave. So all electromagnetic waves are transverse waves.
What are mechanical waves?
e.g. waves on springs, and sound waves, travel through a medium (substance). Mechanical waves may be transverse or longitudinal.
Sound waves are longitudinal.
What is the amplitude of a wave?
The amplitude of a wave is the height of the wave crest to the depth or the wave trough from the position at rest.
What is the relationship between the amplitude of a wave and the amount of energy it carries?
The greater the amplitude of a wave the more energy it carries.
What is the wavelength of a wave?
the wavelength is the distance from one crest to the next crest, or from one trough to the next trough.
What is the frequency of a wave?
The frequency of a wave is the number of wave crests passing a point in one second. The unit of frequency is hertz (Hz). This unit is equivalent to per second (s).
What is the equation for the speed of a wave?
v = f x λ Where: V is the wave speed in metres per second, m/s f is the frequency in hertz, Hz λ is the wavelength in metres, m
What is the wavelength of a longitudinal wave?
The distance from the middle of one compression to the middle of the next compression. (This is the same as middle of rarefaction to middle of next rarefaction)
What is the frequency of longitudinal wave?
The number of compressions passing through a point in a second
Where is the normal drawn?
Perpendicular to the point at which the incident ray hits the mirror
What is the angle of incidence?
The angle between the the incident ray and the normal
What s the angle of reflection?
The angle between the reflected ray and the normal
For any reflected ray, what is the relationship between the angle of incidence and the angle of reflection?
They are equal
Describe the properties of an image in a plane mirror
The image in a plane mirror is:
- The same size as the object
- Upright
- The same distance behind the mirror as the object is in front
- Virtual
What is a real image?
An image that can be formed on a screen, because the rays of light that produce the image actually pass through it.
What is a virtual image?
An image that cannot be formed on a screen as the rays of light that produce the image only appear to pass through it.
What type of waves does refraction occur in ?
Refraction is a property of all waves
What causes refraction ?
Waves change speed when they cross a boundary between different substances. The wavelength of the waves also changes, but the frequency stays the same. The change in speed causes an apparent change in direction. If the waves enter a more dense substance they slow down. If the waves enter a less dense substance they speed up.
However, if the waves travel along the normal, there will not be a change in direction.
What is dispersion ?
When white light is split into a spectrum.
Which colour light is refracted the most?
Violet
Which colour light is refracted the least?
Red
If speed is reduced, in what direction are the rays refracted ?
Toward the normal
If speed is increased, in what direction are the rays refracted?
Away from the normal
What is Diffraction ?
Diffraction is the spreading out of waves when they pass through a gap or round the edge of an obstacle
In what type of waves does Diffraction occur?
Diffraction is a property of all waves
When is the effect of Diffraction most noticeable ?
The effect of Diffraction is most noticeable when the wavelength of the waves is about the same size as the gap or the obstacle.
How are TV signals carried ?
By Radio Waves
Why might people living in hilly areas encounter poor radio and TV signal?
They may not be able to receive the signal as it is blocked by a hill. If the waves do not diffract enough they will be blocked by the hill, meaning the signal will be distorted or lost.
What causes sound ?
Mechanical vibrations in a substance
What mediums can sound travel through?
Solids, Liquids, Gases
In what medium does sound travel the fastest?
Solid
In what medium does sound travel the slowest?
Gases
Sound cannot travel through a vacuum, how can one test this?
Listening to a ringing bell in a ‘Bell Jar’. As air is pumped out of the jar, the ringing sound fades away
What is the frequency range of human hearing?
20Hz-20,000Hz
As a person gets older, what happens to their ability to detect higher frequencies?
It declines
What is produced when a sound is reflected?
an echo
What mediums reflect sound?
Only hard, flat surfaces such as flat walls and floors reflect sound.
What mediums absorb sound?
Soft things like carpets, curtains and furniture absorb sound.
When are sound waves refracted?
Refraction takes place at the boundaries between layers of air at different temperatures.
What instrument is used to show differences in waveform?
An oscilloscope
Although all EMR waves travel at the same speed (In a vacuum), what differs between each type of wave?
Wavelength and Frequency
What makes up the EMR Spectrum (In order of increasing wavelength)
Gamma Rays X-Rays Ultraviolet Visible Infrared Microwaves Radio Waves
What is the range of wavelengths in the EMR Spectrum?
10^-15m(Gamma) - 10 000m (Radio)
What is the relationship between the frequency of EMR waves and the amount of energy it transfers?
The higher the frequency of the wave, the more energy it transfers.
What is the wave speed of EMR Waves in a vacuum?
300 million m/s
Provide an example for the use of
a. ) Microwaves
b. ) Radio Waves
a. ) send signals to and from satellites
b. )Radio and TV signals
What are the dangers of Microwaves and X-Rays?
Microwave radiation and Radio waves penetrate your skin and are absorbed by body tissue. This can heat internal organs and may damage them.
What are Optical Fibres?
Optical Fibres are very thin glass fibres. We use them to transmit signals carried by visible light or infrared radiation. The signals travel down the fibre by repeated total internal reflection.
Why are Optical Fibres used for communications rather than radio and microwave transmissions?
Optical Fibres carry much more information and are more secure than either radio or microwave transmissions.
What is the doppler effect?
If a wave source is moving relative to an observer. The wavelength and frequency detected by the observer will have changed.
E.g. If the source is moving away from the observer, the frequency decreases and the wavelength increases(hence why sirens sound lower pitched when the ambulance is further away).
Define a ‘Galaxy’
A large collection of stars
How do we know that the universe is expanding?
Light observed from distant has been ‘shifted’ towards the red end of the spectrum, demonstrating red shift has occurred. This means the source of light (stars) is moving further away fro earth and therefore, the universe is expanding.
If a source is moving away from the observer what effect will occur?
Red-Shift
If a source is moving toward from the observer what effect will occur?
Blue-Shift
What is the crucial piece of evidence to support the ‘Big Bang Theory’ ?
The presence of Cosmic Microwave Background Radiation (CMBR). The Big Bang Theory is so far the only way we can explain this radiation.
