Flashcards in P1 energy for the home IN PROGRESS Deck (139)
What happens to a substance when it is heated
It gains kinetic energy (KE)
Temperature is a measure of what?
If there is a difference in heat what will happen?
The energy will flow between them
The greAter the heat difference equals what..
Faster rate of cooling or heating.
What does specific heat mean
It tells you how much energy stuff can hold
What is waters specific heat capacity ?
Mass x specific heat capacity x temp change
How do you break intermolecular bonds?
When a substance is condensing or freezing what happens?
Bonds are formed and energy is released
What is specific latent heat
It's the energy needed to change heat
Other formulae for energy
Mass x specific latent heat
Where does conduction occur
Mostly in solids
Define conduction of heat
It is the process where vibrating particles pass on Extra kinetic energy to neighbouring particles
Why do metals conducts heat well.
Because some of their electrons are free to move inside the metal
Where does convection occur
In liquids and gasses
More energetic particles move from hot to cold and take heat energy with them
Radiators in homes what do they do?
Use convection to heat rooms
What is radiation?
Heat from the sun
Name the three ways heat can be transferred
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
What emits radiation?
Are Matt black surfaces good or bad absorber and emitters?
Light coloured smooth and shiny objects are goor or bad are emitting and absorbing?
Bad they reflect but don't absorb or emit
What is heat radiation good for?
What kitchen appliances use radiation
Grills and toasters and microwaves
How can you save money and energy in your home
What is a source?
Something that emits energy or heat such as a radiator
Name 6 ways to insulate your house
Cavity wall insulation
Hot water tank
What's a thermogram
It shows heat and specifically where your house is leaking or losing heat
If a house looks hot ( white yellow and red) what does it mean?
It means the house is losing heat form that area
The total energy output is the same as ...
The energy input
Why is only some of the output energy useful
Some of the input energy is lost or wasted as heat
The less energy wasted equals what..
Efficiency formulae ...
Useful energy output
Total energy input
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
What do waves have (3 things)
What does amplitude mean
Is the height form the rest point of the wave till the crest at the top
What is the wavelength meaning.
It is the length of a full wave from crest to crest
What is wave frequency
It is the number of complete cycles or oscillations passing a certain point per second
Formulae for wave speed...
Frequency x wavelength
One kilohertz =
1000 hertz Hz
All waves can be what...
Reflected refracted and diffracted
What does light reflection do?
It allows us to see objects as the light bounces off them into our eyes
What is the law of reflection?
Angle of incidence = the angle of reflection
What does the total internal reflection depend on?
The critical angle
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
What happens if the incidence angle is equal to the critical angle....
The ray goes along the surface with lots of internal reflection
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
What does diffraction mean
Waves spreading out
The amount of diffraction in a wave depends on what...
The size of the gap relative to the wavelength.
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
How can we communicate with light
What do lasers produce?
Intense beams of monochromic light
It has a low divergence compared to torches and it has a narrow beam
What uses lasers to read digital information
How is infrared used in the home?
Cooking, grilling, toasting, romotecontrols
How are radio waves used?
TV and fm radio
How are microwaves used?
Satellite communication and mobile phones
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
What can ultraviolet radiation cause?
P waves are what....
Longitudinal and goes form side to side or back forth back forth
S waves are what....
Transverse and go up down up down
what does the angle of incidnece equal/
the angle of refelction
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
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
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
waves spreading out
changing the speed of a wave changes its direction
what caused waves to travel at differnt speeds?
the densities of objects (from glass to air a wave speed changes)
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)
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
what is the rule for refaction, when is the only time it happens?
when the wave meets the new medium at an angle.
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
as we go along the spectrum form radio waves to gaa rays, what haopnes/
the frequecy incrases
the wavelength decreases
what do properies of the em waves depend on/
the frequency and wave length
what happnes to em waves when the frequency and length changes
its interaction with matter changes also
(how is asorbed, refected or transmitted)
as a rule what can the waves at each end of the em spectrum do?
pass through materials
as a rule what can the waves at the middle of the em spectrum do/
shorter wavelength/ higher frequency menas the wave is more....
dangerous to living cells as they have more enrgy
what happns if an Em radiation is asorbed?
can cause heating and ionisation
when an atom or molecule either loses or gains electrons and its dangerous
how are em waves used?
cooking heating communication
what has to happen to the waves before they can be used for communication?
they have to be changed into an electrical signal
why is it good to use light waves for signal?
they travel fast
why are electrical wires and optical fibers good for signals
they can cary lots of information
cables cant be tapped into
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
whats a disadvantages of cabled signals?
they can be hard to repair
what does communicating with light require?
what is the most universally know example of light communication?
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
in modern light communication , what does it travel through
optical fibers, they carry data over long disances as pulses of light or infared radiations
how do optical fibers work?
waves bounce off the sides of a very narrow core which is protected by outer layers
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.
how are optical fibers used?
telephone and broadband internet cables
medical purposes( see inside the body without operation)
artificial christmass trees /lights
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
lots of different signals can be transmitted down a single optical fibre
what is a laser?
a narrow intense bean of monchromatic light
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
all one single pure colour
what are the waves like in a laser?
all the same frequency and wavelength
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
whatis a lasers divergence like?
low, the beam stays narrow even at a long distnace and it doesnt divergent like a normal torch does
what household object uses lasers?
cd players use them to read digital information
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
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.
how is infared used in the home?
transmitions between computers and phones
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
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.
who use infared to monitor temperature?
police and the military to spot people on the lose running away
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
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.
what is a properly of radio and microwaves?
they are good at transfering information over long distances
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
what is the common use of radio waves?
what defines a radio wave?
em radiation with wavelenths longer than baout 10cm
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.
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
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
what alters signal strength?
what does the amount of diffraction depend on?
the wavelength of the wave, relatve to the size of gap or obstacle
do long wavelength waves have lots of diffraction or not?
yes as they are large compared with the gap or obstacles
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
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
what results in signal loss?
diffraction at the edges of dishes used to transmit signlas, the wave spreads out and the signal becomes weaker
what type of ladscape is not good for recieving shorter wavlengths radio and microwaves?
what do long waves do in terms of diffraction?
bend around the earth and get diffracted alot
what can help radio waves travel further?
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
how can refraction help a wave travel further?
if it happens high up in the atmosphere it helps with long distance communication
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.
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.
what does the amount of refraction in the ionosphere depend on?
frequency and angle of elevation
what does it mean to bounce off the ionsphere?
its similar to how light waves are totalling internally reflected inside optical fibers
whats problem with refraction?
it can disrupt a signal by bending it away form the reciever dish
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
why is there lots of interfrence between radio waves?
similar waves covering a simiar areas ca combine to create noise,
why are radio stations that are near to each other use different frequencies?
it stop interfrence
what does the reciver of radio waves do?
separate the waves