Flashcards in P1 energy for the home IN PROGRESS Deck (139)
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What happens to a substance when it is heated
It gains kinetic energy (KE)
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Temperature is a measure of what?
Hotness
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If there is a difference in heat what will happen?
The energy will flow between them
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The greAter the heat difference equals what..
Faster rate of cooling or heating.
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What does specific heat mean
It tells you how much energy stuff can hold
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What is waters specific heat capacity ?
4200 j/kg/Celsius
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Energy=
Mass x specific heat capacity x temp change
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How do you break intermolecular bonds?
Use heat
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When a substance is condensing or freezing what happens?
Bonds are formed and energy is released
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What is specific latent heat
It's the energy needed to change heat
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Other formulae for energy
Mass x specific latent heat
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Where does conduction occur
Mostly in solids
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Define conduction of heat
It is the process where vibrating particles pass on Extra kinetic energy to neighbouring particles
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Why do metals conducts heat well.
Because some of their electrons are free to move inside the metal
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Where does convection occur
In liquids and gasses
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Define convection
More energetic particles move from hot to cold and take heat energy with them
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Radiators in homes what do they do?
Use convection to heat rooms
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What is radiation?
Heat from the sun
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Name the three ways heat can be transferred
Conduction
Convection
Radiation
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What makes radiation different
It does not need a material to travel in fin works in a vacuum
It only happens in transparent things such as air, glass and water
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What emits radiation?
All objects
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Are Matt black surfaces good or bad absorber and emitters?
Good
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Light coloured smooth and shiny objects are goor or bad are emitting and absorbing?
Bad they reflect but don't absorb or emit
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What is heat radiation good for?
Cooking
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What kitchen appliances use radiation
Grills and toasters and microwaves
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How can you save money and energy in your home
Insulation
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What is a source?
Something that emits energy or heat such as a radiator
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Name 6 ways to insulate your house
Loft insulation
Cavity wall insulation
Draught proofing
Thick curtains
Double glazing
Hot water tank
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What's a thermogram
It shows heat and specifically where your house is leaking or losing heat
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If a house looks hot ( white yellow and red) what does it mean?
It means the house is losing heat form that area
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The total energy output is the same as ...
The energy input
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Why is only some of the output energy useful
Some of the input energy is lost or wasted as heat
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The less energy wasted equals what..
Higher efficiently
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Efficiency formulae ...
Useful energy output
-------------------------- (X100%)
Total energy input
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What is a sankey diagram
It shows energy transformations. It shows how much of the input energy is useful at the end and how much is being wasted
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What do waves have (3 things)
Amplitude
Wavelength
Frequency
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What does amplitude mean
Is the height form the rest point of the wave till the crest at the top
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What is the wavelength meaning.
It is the length of a full wave from crest to crest
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What is wave frequency
It is the number of complete cycles or oscillations passing a certain point per second
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Formulae for wave speed...
Frequency x wavelength
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One kilohertz =
1000 hertz Hz
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1megahertz =
1000000 hertz
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All waves can be what...
Reflected refracted and diffracted
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What does light reflection do?
It allows us to see objects as the light bounces off them into our eyes
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What is the law of reflection?
Angle of incidence = the angle of reflection
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What does the total internal reflection depend on?
The critical angle
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What happens if the angle of incidence is less than the critical angle...
Most of the light is refracted into the outer layer but some is internally reflected
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What happens if the incidence angle is equal to the critical angle....
The ray goes along the surface with lots of internal reflection
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What happens if the incidence angle is bigger than the critical angle....
No light comes out as it is all internally reflected so total internal reflection
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What does diffraction mean
Waves spreading out
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The amount of diffraction in a wave depends on what...
The size of the gap relative to the wavelength.
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Name the 7 types in em wave s
Grumpy. Gamma rays
X men. X rays
Urinate Ultra violet
Violently. Visible light
In infa red
My micro waves
Room radio waves
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How can we communicate with light
Morse code
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What do lasers produce?
Intense beams of monochromic light
It has a low divergence compared to torches and it has a narrow beam
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What uses lasers to read digital information
CD players
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How is infrared used in the home?
Cooking, grilling, toasting, romotecontrols
Phones
Computers
Securing systems
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How are radio waves used?
In communications
TV and fm radio
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How are microwaves used?
Satellite communication and mobile phones
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What is the difference between anolauge and digital waves
Analogue is wavy and takes many values in range
Digital is just on or off with only two values
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What can ultraviolet radiation cause?
Skin cancer
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P waves are what....
Longitudinal and goes form side to side or back forth back forth
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S waves are what....
Transverse and go up down up down
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what does the angle of incidnece equal/
the angle of refelction
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what does the amount of diffraction depend on?
the size of the gap relative to the wavelength. the narrower the gap or the longer the wavelength, the more the wave will spread out
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does ligt have a large or small wave length, what does this mean in terms of diffraction?
it is very samll (about 0.0005mm) soitt can be diffracted but needs a very small gap
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what does a long shaddw show in terms of diffractions and wave length?
the shaddow is where the wave is blocked. the wider the obstacle compared to thewavelength the less diffraction so a longer shaddow
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define diffraction
waves spreading out
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define refraction
changing the speed of a wave changes its direction
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what caused waves to travel at differnt speeds?
the densities of objects (from glass to air a wave speed changes)
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if a light wave hits the boundry between to substances face on what happens?
it changes spped but carries on in the same direction (now has shorter wavelength but same frequency)
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if a light wave hits the boundry between to substances at an angle what happens?
part of the wave hits the new density changes speed. the other part carries on at the first spped for a while so the wave changes direction. it has been REFRACTED
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what is the rule for refaction, when is the only time it happens?
when the wave meets the new medium at an angle.
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do all forms of electromagnetic waves travel at the same speed through a vacuum?
yes, this menas waves with a shorter wavelength have higher frequencies
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as we go along the spectrum form radio waves to gaa rays, what haopnes/
the frequecy incrases
the wavelength decreases
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what do properies of the em waves depend on/
the frequency and wave length
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what happnes to em waves when the frequency and length changes
its interaction with matter changes also
(how is asorbed, refected or transmitted)
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as a rule what can the waves at each end of the em spectrum do?
pass through materials
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as a rule what can the waves at the middle of the em spectrum do/
be asorbed
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shorter wavelength/ higher frequency menas the wave is more....
dangerous to living cells as they have more enrgy
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what happns if an Em radiation is asorbed?
can cause heating and ionisation
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define ionisation
when an atom or molecule either loses or gains electrons and its dangerous
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how are em waves used?
cooking heating communication
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what has to happen to the waves before they can be used for communication?
they have to be changed into an electrical signal
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why is it good to use light waves for signal?
they travel fast
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why are electrical wires and optical fibers good for signals
they can cary lots of information
its secure
cables cant be tapped into
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whats a bad point about using radio waves for signals/
they travek in the air so can be interceped easilt, no secure, this is a problem for wireless internet networks
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whats a disadvantages of cabled signals?
they can be hard to repair
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what does communicating with light require?
a code
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what is the most universally know example of light communication?
morse code
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how does morse code work?
it sends on-off signals realed between stations far away by flashing a light on and off.
the dots and dashes of pulses of light are decoded into letters and numbers.
...---... = SOS
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in modern light communication , what does it travel through
optical fibers, they carry data over long disances as pulses of light or infared radiations
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how do optical fibers work?
waves bounce off the sides of a very narrow core which is protected by outer layers
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how does a ray of light enter n optical fiber?
so that it hits the boundry between the core and outer cladding at an angle greater than the critical angle for the material. this causes total internal reflection of the ray once inside the core.
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how are optical fibers used?
telephone and broadband internet cables
medical purposes( see inside the body without operation)
artificial christmass trees /lights
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what are the advantages of using ligh as a form of communication?
it is very quick
doesnt need any cables
little interference (its a digital signal0
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define multiplexing
lots of different signals can be transmitted down a single optical fibre
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what is a laser?
a narrow intense bean of monchromatic light
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what des it mean to say daylight is out of phase?
its a combination of of differnt frequency and wavelngth (and so colour) waves that are all out of phase with each other.
the crests and throughs dont match
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define monochromatic
all one single pure colour
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what are the waves like in a laser?
all the same frequency and wavelength
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what makes a laser so intense?
the light waves are all in phase (the trought and crests line up) increasing the amplitude thus creating an intense beam
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whatis a lasers divergence like?
low, the beam stays narrow even at a long distnace and it doesnt divergent like a normal torch does
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what household object uses lasers?
cd players use them to read digital information
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how is a laser used in a cd player?
the suface of the cd had many shallow pits cut into it, a laser is shone onto the cd and refected off the shiy bottom surface as it spins. the pots cause differnt refection and this is picked up by a sensor and changed into an electrical signal
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what do the pits and lands in a cd represent?
digital ons and offs
a change in refecled bean menas an on whilstt no change is an off.
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how is infared used in the home?
cooking (grills/toasters)
remote controls
transmitions between computers and phones
security systems
optical fibers
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how is infared used to monitor temperature?
infared is also knows a heat readiation as it is given out by hot objects. infared sensors can pick this radiation upand monitor temperatures
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how is the infared radiation in obkects picked up by the sensors and changed into a picture?
its turned into elictrical signals that are displayed ona screen as a picture. the hotter the object the brighter.
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who use infared to monitor temperature?
police and the military to spot people on the lose running away
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how do remote controlers work is controling electrical equipment?
the emit pulses of infared radiation, the pulses act as a digiatal (on/off) code which the device will detect and decode int instructions
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whata drawback to using infared in remote controlers?
you have to be close to the device your operating as the radiation is weak.
the bean has to be pointed directly at the detector as the waves only travel in straight lines.
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what is a properly of radio and microwaves?
they are good at transfering information over long distances
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why are radio and microwaves good at travelng long distnaces?
they dont get asorbed by the ears atmosphere as much as waves in the middle of the spectrum
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what is the common use of radio waves?
communication
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what defines a radio wave?
em radiation with wavelenths longer than baout 10cm
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why are long-wave radio waves good?
they can be trasnsmitted form one plave and recived halfway roud the would as they diffract(bend) aroud the curved surace of the earth.
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when radio waves are used for tv and fm radio what size are the wavelengths?
short. to get reception you must be in direct sight of the transmitter as the signal wont bend around hills or travel far through bulidings
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why are short radio signals used, why are they handy?
they can be recieved at long ditances form the transmitter because of reflection in the ionosphere
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what alters signal strength?
diffraction
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what does the amount of diffraction depend on?
the wavelength of the wave, relatve to the size of gap or obstacle
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do long wavelength waves have lots of diffraction or not?
yes as they are large compared with the gap or obstacles
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what does it mean for long wavelengths to be diffracted alot, how is it helpful with signals?
they are able to bend around corners and obstacles, thus they can travel long distances between the transmitter and reciever without being in the lie of sight with each other
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why are shorter wave lengths radio waves and microwaves not so handy for signals?
they dont diffract very much so they transmitter needs to be high up to avoid obstacles , they waves cant travel very far either
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what results in signal loss?
diffraction at the edges of dishes used to transmit signlas, the wave spreads out and the signal becomes weaker
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what type of ladscape is not good for recieving shorter wavlengths radio and microwaves?
mountinous areas
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what do long waves do in terms of diffraction?
bend around the earth and get diffracted alot
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what can help radio waves travel further?
refraction
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whats refraction?
whena wave comes up against something of a differnet density it changes speed. it it hits the new density at an angle it changes direction
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how can refraction help a wave travel further?
if it happens high up in the atmosphere it helps with long distance communication
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define the ionosphere?
uv radiation form the sun creates layers of ionised atoms in the earths atmosphere, these atms are electically charged and create the ionosphere.
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how does the ionosphere help with refraction?
radio waves travel faster through ionisded parts of the atmosphere and this causes refraction, they bounce back to earth an are refectedthe most in this ionsophere.
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what does the amount of refraction in the ionosphere depend on?
frequency and angle of elevation
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what does it mean to bounce off the ionsphere?
its similar to how light waves are totalling internally reflected inside optical fibers
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whats problem with refraction?
it can disrupt a signal by bending it away form the reciever dish
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why dor adio stations use waves of very similar frequencies?
there is a limited number of radio waves frequencies that can be used to transmit a good analogue saignals so they use lots of similar waves
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why is there lots of interfrence between radio waves?
similar waves covering a simiar areas ca combine to create noise,
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why are radio stations that are near to each other use different frequencies?
it stop interfrence
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what does the reciver of radio waves do?
separate the waves
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