Flashcards
PHYSICS MODULE 1
Flashcards do conjunto (35)
- 1what is specific heat capacity ?A measurement of how much energy an object can store
- 2It takes 5000J to heat up 50g of a substance by 40C. Calculate its specific heat capacity.ENERGY = MASS (kg) x SHC x TEMP CHANGE
Rearrange the equation.
5000J / 0.05g x 40C = SHC
SHC = 2500 J/Kg/C - 3Explain why heating a pan of boiling water doesn't increase its temperature.heating a solid causes particles to vibrate faster until the forces between particles are broken and the object begins to melt.
When the substance is melting your putting in energy that is breaking the intermolecular forces rather than increasing the temp - 4how much energy is need to boil dry pan of 500g of water at 100C? (The Specific latent heat of water is 2,260,000 J/Kg)Energy = mass x SLH
DIVIDE BY 1000
0.5 x 2,260,000 = 1,130,000 J - 5describe how heat is transferred through a) conduction b) convection c) radiationa) Happens in only solids - vibration of particles carries the heat to cooler particles
b) Only in liquid - particles vibrate and become less dense - warm less dense particle begin to rise - cooler fluid heat up
c) Heat from sun - travel in straight line - infrared radiations - travels through a vacuum - only occurs in transparent objects - 6Describe how heat radiation is used to cook food a) in a grill b) in a mircrowavea) Uses infrared radiation - absorbed by the surface of food - increases kinetic energy - convection/ conduction occurs
b) uses microwave radiation- penerates 1cm into outer layer - absorbed by water or fat molecules - increases kinetic energy - convection/ conduction occurs - 7Describe three ways of saving energy at home and how they work1) thick curtains - reduce heat loss
2) double glazing -reduce heat loss
3) loft insulation - reduces heat loss - 8why is it more useful to have a light coloured fridge and dark coloured radiator ?Because light smoot and shiny colours dont absorb or emit heat radiation
whereas dark matt colours are very good at absorbing heat radiations - 9how much energy is wasted if a hairdrier thats 20% efficient has a total energy input of 200,000 JEFFICIENCY = useful energy output / total energy input
REARRANGE
useful energy output = efficiency x total energy input
0.2(20%) x 200,000 = 40,000
wasted energy = 200,000 - 40,000 = 160,000 J - 10what happens to a wave when its.. a) diffracted b) refracted c)reflecteda) when a wave passes throw a gap and spreads out
b) when an angle passes goes from a less dense object to more dense object and its speed decreases
c) when the critical angle bounces of a smooth surface
(critical angle = angle of reflection) - 11eva is building a sandcastle. she estimates that 1 wave passes her sandcastle every 2 sec, and the crest of the wave are 90cm apart. calculate the speed of the waves.Wave speed(m/s) = frequency (Hz)x wavelength (m)
0.5 x 0.90 = 0.45 m/s
(freq = a no. of complete waves per second.. 1 wave = 2 sec so 1/2 wave is 1 sec) - 12what effects the amount of diffraction occuring ?the size of the gap
- 13explain how the size of the gap can effect diffractions a) A gap that is much wider than wavelength b) a gap that is a bit wider than wavelength c) a gap that is the same size as wavelengtha) little diffraction
b) diffraction only at edges
c) maximum diffraction occurs - 14list the 7 types of electromagnetic waves in order of wavelength (smallest to largest)1) Radio waves
2) microwaves
3)infrared
4)visible light
5)ultraviolet
6) x-rays
7)gammas rays - 15explain why morse code is in a digital signalAs the light pulse is only either "on" or "off"
- 16describe how light signals can travel in optical fibres ?-the light rays enter the fibres so it hits the boundary between the core and the outer layer cladding at an angle greater than the critical angle.
- this causes the total internal reflection - 17what are the advantages of using light ?- very quick
- its multiplexing (lots of signals can be transmitted through a single optical fibre)
- its a digital signal - 18explain the properties of laser beams which make them a) monochromatic b) coherenta) they are a visible light that have the same frequency and wavelength this makes them monochromatic (1 single pure colour)
b) they are all in phase - the trough and crest line up increasing the amplitude so producing intense beam - 19describe how layers are used in CD players ?1. laser shone on the CD is reflected from the shiny bottoms surface spinning
2. the beam is reflected from land and pit differently causing light sensor to pick this up
3. the change in the reflected beam represent the on and off digital signal
4. an amplifier and a loudspeaker convert the electrical signals into sound of the right pitch and loudness - 20explain how infrared radiation is used to control electrical equipment ?eg : remote control EMIT PULSES of infrared radiation
the pulses act as digital signals
the device detects and decode the pattern of pulses coming from the remote and follows the code instruction - 21give examples of electrical devices that use infrared radiation to control them.- cooking , grills and toasters
- remote control transfers information to TV's and DVD players
- transmit info from mobile to computer
- security systems (sensor lights)
- could be used in optical fibres - 22explain why long-wave radio waves can bend around obstacles ?because they have longer wavelengths they are bigger than the gap of diffraction this means they are able to bend. that is why they can travel long distances between the receiver and the transmitter without being in the line of sight
- 23what happens to the radio waves in the ionosphere ?ionosphere are layers of electrically charged ionised atoms that have either gain or lost electrons in the earths atmosphere. radio waves travel faster through the ionised atoms. the short waves are refracted most in the ionosphere so they can travel back to earth long way form the transmitter
- 24how does digital audio broadcasting work different to other radio stations ?- its digital signals
-transmitted over a relatively small frequency and separated out by the receiver
- DAB has many different signals compressed then transmitted as single wave - 25give two advantages and two disadvantages of DAB radios ?advantages
- less interference than traditional radio stations.
- multiplexing meaning increase in the potential number of radio stations available
disadvantage
-limited numbers of DAB radio station so some areas cant receive the digital signal
-even if you receive it the sound quality wouldn't be as good due to the compression of the signals - 26describe how satellites are used for communication ?communication from and to satellites uses microwaves signals so it can pass through the earth watery atmosphere without being absorbed too much. the satellite orbits the earth, picking up signals and transmitting them back to a satellite on earth.
- 27why are microwave transmitters located in high places and close together ?mobile phone also use microwaves, the transmitter passes signals between each other , then back to your mobile phone.
microwaves have short wavelengths so they don't diffract much, so they're easily blocked by large obstacles. that is why transmitted need to be located in high places and in line of sight. - 28explain why scientist are concerned about the dangers of: a) a mobile phone use b) the thinning of ozone layera) microwave can be absorbed by water molecules (eg. microwave ovens), so if cell tissue absorbs microwave the cell may be burned or kills and could damage your health.
b) The ozone layer protects us from UV radiation, if the ozone is broken by the CFC's we are no longer being protected. this means that is it easy to get skin cancer. - 29explain how diffraction affects the size of receiver needed to pick up different wave signals.when a wave is transmitted it passes through a gap, the size of the gap determines how big the wave is going to be.
so if the gap is smaller than the wave, the wave will spread more and some signals will be lost, however if the gap is the same size as the wave there is going to be less diffraction. so the receiver wouldn't have to be so big therefore the size of the receiver is determined by the size of the wave after passing through a gap. - 30explain the different between analogue and digital.analogue - can take any value. the amplitude and frequency of an analogue vary continuously
digital - can only take two values. the values tend to be on and off or 1/0. - 31what are the advantages of digital signals over analogue?- you can transmit several signals at the same time using just one cable. (multiplexing)
- the noise is easier to remove or ignore in digital than in analogue so they stay high quality - 32why are CFC's bad ?CFC's are gases which react with the ozone layer and break it down causing us to being exposed more to the UV radiations.
- 33how does the sun protection factor work ?if you have a sun cream with SPF 15, this means you could stay in the sun for as 15 times more than you would have if you weren't wearing sun creams
- 34alexis normally burns after 40 minutes in the sun. before going to the beach, she applies sunscreen with SPF 8. For how long can she sunbathe before she will start to burn?Time = 40mins
SPF = 8
40 mins x 8 = 320 mins
convert
320 mins = 5 hours and 20 mins - 35name and describe two types of wave produced by earthquakesP.waves
- they're longitude
-travel though solid and liquids
- they're faster than S.waves
S.waves
- they're transverse
- they only travel through solids
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- FlashCards sobre PHYSICS MODULE 1 , criado por Vicky Grudzinska em 19-03-2016.
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- Vicky Grudzinska
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