# P1 OCR Energy for the home

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• Created by: gmclaren
• Created on: 08-11-15 13:33
What is the definition of heat?
A measurement of energy
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What is the definition of temperature?
Average kinetic energy of all particles
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A cup of tea is 80 degrees and a bath is 40 degrees, which one has more heat and why?
The bath because the more more there is the more heat there is
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A cup of tea is 80 degrees and a bath is 40 degrees, which one has more temperature?
The cup of tea
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What is the definition of a thermogram?
A picture that detects the heat of an object
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On a thermogram which colour is hot?
Red/white
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On a thermogram which colour is cold?
Blue
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A person has just come from a warm house and is now stood in the snow, why does he loose his heat energy quicker?
Because the bigger the temperature difference is the quicker the heat temperature will flow
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What is the definition of SHC?
How much heat is needed to raise 1 kg of a material by 1 degrees
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What happens if something has a high SHC?
It will take in a lot of heat without the temperature going down too much and it gives out a lot of heat without the temperature dropping too much
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What is a use of something that has a high SHC?
A hot water bottle or ice pack
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What happens if something has a low SHC?
It's temperature rises quickly without too much heat being added and it's temperature drops drastically when it gives out a small amount of heat
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What is the equation for SHC?
Energy = mass x SHC x temperature change
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What is the definition for SLH?
Amount of energy needed to change the state of 1 kg of material
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What is vaporization?
Liquid to gas
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What is latent heat of fusion?
Solid to liquid
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Which method requires more energy - vaporization or latent heat of fusion and why?
Vaporization because more energy is needed to break/make bonds between liquid/gas then solid/liquid
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What is the equation for SLH?
Energy = mass x SLH
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Does the temperature change when something is changing state? Why/why not?
The temperature does not change because all the energy is being used to change the state of the material
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What type of surfaces are good at emitting and absorbing radiation?
Dark matte
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What type of surfaces are good at reflecting radiation?
Silver shiny
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Why can radiation pass through air?
Because it is a wave not a particle
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Why is a vacuum flask good at keeping heat in it?
Because it stops heat travelling by conduction, convection and radiation. It has a silver coating on the inside so the radiation waves reflect off the surface, it has a vacuum between the double wall which stops convection and conduction
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What is conduction?
Conduction occurs when particles gain Kinetic Energy. They then pass their KE on to other particles via collisions
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What is convection?
Particles that gain Kinetic Energy and move around more, until they are far apart. This makes the liquid/gas less dense and so the particles rise
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How do curtains reduce heat loss?
They absorb infrared radiation before it can pass through the curtains
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How does double glazing reduce heat loss through conduction?
There is a layer of trapped air between two panes of glass, this works because trapped air is a bad conductor because the particles are so far apart it is hard to pass heat on, this stops any conduction.
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How does double glazing reduce heat loss through convection?
The trapped air between the two glass panes is trapped meaning it is hard for particles to move around, this reduces convection
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How does draught proofing reduces heat loss?
It blocks any gaps that particles might get through, reducing conduction
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How does cavity wall insulation reduces heat loss?
A layer of insulating material (mostly trapped air) is inserted between two walls, reducing conduction and convection
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How does shiny foil reduces heat loss?
The shiny foil helps reduce radiation, because it reflect the waves back trapping them
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What is the equation for payback time?
Payback time = cost to install/money saved per year
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What is the definition of efficiency?
A measurement of how much energy that goes into a device is useful
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What is the equation for efficiency?
Efficiency = useful energy output/total energy input x 100
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What are oscillations?
The vibrations in waves
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What are transverse waves?
Oscillations at 90 degrees to the direction
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What are longitudinal waves?
Oscillations at the same direction to the wave
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What is amplitude?
Maximum height of the wave measured from the middle
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What is frequency?
The number of waves passing one point per second
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What is the equation for wave speed?
Frequency x wavelength
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What is the anagram for electro-magnetic waves?
Ronald makes instruments, like ukulele's, xylophones and giutars
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What happens to energy as you go up the EM scale?
The waves increase in energy
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What happens to frequency as you go up the EM scale?
The waves increase in frequency
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If the angle of incidence is 10 degrees, what is the angle of reflection? And why?
10 degrees because the angle of incidence is always equal to the angle of reflection
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If the new medium is less dense, what happens to the speed of the wave?
It speeds up and bends away from the normal
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If the new medium is more dense, what happens to the speed of the wave?
It slows down and bends towards the normal
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What makes diffraction bigger?
The longer the wavelength, the smaller the gap or if the wavelength and the gap are the same size
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What is one problem caused by diffraction?
If the light passes through a telescope it diffracts and causes a blurry image
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What must happen for total internal reflection to occur?
When the angle is above the critical angle for the material and when the light is travelling in the denser of two materials
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Give two uses of fibre optics.
Endoscopy and TV
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How do the waves travel in fibre optics?
The waves travel in a glass fibre by total internal reflection
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How do endoscopes work?
The light reflects down the glass fibre and illuminates the patients body, then travels back up, allowing the doctor to see via the tube or via TV
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List three types of signal communication
Smoke signals, flashing lights and morse code
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List three properties of lasers.
Goes over long distance, narrow beam and just one colour
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What are two things that lasers can be used for?
Surgery and dental treatment and CD, DVD, Blu-ray
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What does the term 'in-phase' mean?
There crests and troughs all line up
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How does reading a CD work?
There are millions of pits on the CD so the laser reads this and where there aren't pits there is no reflection, but where there are pits it reflects an image, this is similar to morse code
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The warmer the object...
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How does a toaster heat an object?
The toaster absorbs the infared radiation and this transfers to the food, cooking the surface area
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Why do we get a crispy layer on toast?
The water evaporates
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How does a microwave heat an object?
Microwaves travel 1cm into the food, the water and fat molecules absorbs the heat and is cooked
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Why is the microwave lined with silver?
So the food reflects off the silver and hits the food
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How is the food heated?
By convection and conduction
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Why does metal mesh outline the front of the microwave
To protect humans from getting burnt
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Which cooks faster, microwaves or toasters, and why?
Microwaves cook faster because they have a higher frequency, so more energy and they penetrate deeper into the food
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Name two uses of microwaves?
Mobiles and Microwaves
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Why do you often lose signal on your mobile? What do you need to make this signal stronger?
Because microwaves can't diffract very well, a line of sight
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Why do you not lose signal often with the radio?
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Transmitters should be...
High up with no obstacles in the way
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How do digital signals work?
They have two values, on (1) or off (0), these values equate to a series of pulses
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How do analogue signals work?
They constantly change, like adjusting a light
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Which signal is better and why?
Digital because you can cancle out any background noise and you can send multiple signals at one (multiplexing)
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What is one drawback of DAB?
Not all of the UK can get it
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What wave is an example of digital signal?
Infared
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Give two uses of infrared digital signal
Burglar alarms to detect body heat and remote controls
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List some drawbacks and advantages of wireless communication
Needs an areal, portable, can use anywhere, no wires
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Why might signals lose energy?
If they are reflected and refracted over a long distance
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How do signals travel over really long distances?
They are reflected over an ionosphere (total internal reflection) or they are sent to a satelitte
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What causes an earthquake?
We have plates under the earth that have small cracks in them, when these plate grind and bump into each other they can cause a build up in pressure, eventually one plate will slip and an earthquake will happen
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What are P-waves and what are three properties?
They are a type of seismic wave and they travel very fast through solid and liquid, they are longitudinal waves
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What are S-waves and what are three properties?
They are another type of seismic wave and they travel slower than P-waves and only go through solid, they are transverse waves
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How do S-waves support the theory of the earths structure?
After an earthquake S-waves are only detected in some places, never in the middle of the earth, this provides evidence for the earth having a molten core
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Why does ultra violet have a high energy?
Because it has a short wavelength and high frequency
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How does sun cream protect the skin against UV rays?
Sun cream absorbs the UV rays, meaning the skin underneath is not damaged
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Why does darker skin not need as much sun cream?
The darker your skin is the more ultra-violet is absorbed at the surface, protecting the cells beneath
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What does the Ozone do?
It is a gas protecting us from harmful powerful UV rays
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What id scientist discover in the 1980s?
There was a hole in the ozone layer cause by Chloroflurocarbons (cfcs)
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## Other cards in this set

### Card 2

#### Front

What is the definition of temperature?

#### Back

Average kinetic energy of all particles

### Card 3

#### Front

A cup of tea is 80 degrees and a bath is 40 degrees, which one has more heat and why?

### Card 4

#### Front

A cup of tea is 80 degrees and a bath is 40 degrees, which one has more temperature?

### Card 5

#### Front

What is the definition of a thermogram?