P1, P2, P3
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- Created by: ikrolivia
- Created on: 25-11-15 18:50
What is heat measured in?
Joules
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Heat is a measurement of energy on an.....
Absolute scale (always joules)
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The amount of energy needed to raise temp of something depends on what 3 things?
Mass, material & change required
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What is specific heat capacity?
How much energy a material can hold
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What does specific latent heat depend on?
material & state
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During melting and boiling of water, the energy supplied is used to...?
break intermolecular bonds
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What are conductors?
Materials that allow energy to flow through them quickly
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What are insulators?
Materials that allow energy to flow through them slowly (e.g. non-metals)
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Why are curtains good insulators?
Because they trap a layer of air between them and the window, which helps reduce energy loss
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Methods of insulation
fibreglass, foam cavity wall insulation, double-glazing, draught excluders & reflective foil on walls
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Cavity wall insulation:
Made up of inner/outer wall, separated by cavity filled with air, trapped air good insulator, cavity free. Heat passes through by conduction. This heats air in cavity. Heat is then carried away by convection. Foam has trapped air so heat loss reduced
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What is energy efficiency?
A measure of how good an appliance is at converting input energy into useful output energy
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Conduction
transfer of heat energy through a substance from hotter region to cooler region without any movement of substance itself
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Convection
transfer of heat energy from hotter regions to cooler regions by movement of particles
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Radiation
infrared radiation is an electromagnetic wave and needs no medium
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Give an example of a transverse wave
Light
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A transverse wave has what?
Amplitude, wavelength & frequency
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What is the electromagnetic spectrum?
A continuous spectrum that extends beyond each end of the visible spectrum for light
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Electromagnetic spectrum in order
Radio waves, microwaves, infrared rays, visible light, uv rays, x-rays, gamma rays
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The wave equation (to find out wave speed)
frequency x wavelength
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What is meant by refraction?
A wave speeds up or slows down as it passes from one medium to another.
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What is diffraction?
As waves pass through a gap or an opening, edges spread out
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Maximum diffraction
Occurs when the gap is same width as wavelength of wave passing through it. This limits quality of image produced by telescopes/optical microscopes
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Wireless technology advantages
signals available 24/7, no wiring needed, portable & convenient
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What type of signal do optical fibres carry?
Binary code (digital)
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Pros/cons of using light as a signal
+ travels fast +small loss of signal - can't be used for wireless signalling, doesn't diffract well
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pros/cons of using electrical signals
+ can be sent along wires - signal deteriorates
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pros/cons of using radio waves as a signal
+ waves diffract around obstacles - diffraction leads to signal loss
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Lasers make a beam of light in which all light waves...?
have same frequency, are in phase with each other, have low divergence
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What does the amount of radiation absorbed from a surface depend on?
surface temp, colour & texture
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Microwaves...
ABSORBED by water/fat molecules, PENETRATE 1cm, REFLECTED by shiny metal, TRAVEL through glass n plastics
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Infrared rays...
heat surface of food, absorbed by black, reflected off shiny objects
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How can microwave signals be affected?
large obstacles / curvature of Earth / poor weather conditions / interference between signals
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How can these problems be reduced?
limiting distance between transmitters / positioning masts on hills
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In which devices is infrared used in?
tv remotes, burglar alarms, security lights, door sensors, short-distance wireless data links
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Analogue signals
Used to transmit data. Vary continuously in amplitude. Suffer from interference in form of noise.
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Digital signals
Also used to transmit data in series of pulses. Don't vary- have 2 states. Interference doesn't affect digital signals.
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Advantages and disadvantages of wireless communication
+ no connection to phone landline needed + portable, convenient, allows access anywhere // - aerial needed to pick up signal
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What is the ionosphere?
Electrically charged layer in Earth's upper atmosphere. Longer wavelength radio waves are reflected by ionosphere.
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What does DAB stand for?
digital audio broadcasting
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Advantages of DAB
more stations available / less interference w broadcasts from other stations
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Disadvantages of DAB
audio quality not as good as FM / some areas can't get DAB
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What are the names of the shock waves that earthquakes produce?
Seismic
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What are the 2 types of seismic wave?
S-waves (transverse & travel through solids) P-waves (longitudinal & travel through solids and liquids)
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3 factors that contribute to global warming
deforestation / increased co2 emissions from fossil fuels / increased energy use in homes and industry
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Weather patterns are affected by human activity, as well as by natural phenomena, for example...?
volcanic dust reflects radiation from sun back to space causing COOLING / factory dust reflects radiation from cities back to Earth, causing WARMING
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What does the sun produce?
Electromagnetic waves
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How can you reduce the risk of getting skin cancer?
stay out of midday sun / cover skin / avoid sun beds / use sunscreen
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What is the ozone layer??
A gas found naturally high up in atmosphere which stops too many harmful uv rays reaching Earth
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What do scientists do to study the ozone layer?
repeat experiments w new equipment / consider data from other scientists who replicated experiments / test their predictions based on current explanations
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The discovery of the hole in ozone layer over Antarctica had what impacts globally?
Legislation passed in countries to ban use of CFCs in fridge cooling systems / old fridges & freezers w CFCs must be disposed of / CFCs no longer used as propellants in aerosol cans
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What do photocells do?
capture light energy from Sun on flat silicon surfaces. Energy then transformed into electric current which goes in same direction all the time. Known as direct current
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Advantages of photocells
use renewable energy / no need for fuel / no pollution / have long life / little maintenance required / operate in remote locations
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Disadvantages of photocells
no power at night or in bad weather / expensive / take up space
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What does the power of a photocell depend on?
surface area, intensity of light, distance between light source and photocell
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Advantages of wind turbines
wind is renewable / it's free after set-up / no pollution
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Disavantages of wind turbines
Visual pollution / need loads of space / dependent on wind so unreliable
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What does the 'dynamo effect' refer to?
The way in which electricity is generated
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How can this electricity be generated?
moving wire near magnet // OR // moving magnet near coil of wire
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How can current generated be increased?
stronger magnets / more turns in coil / turn coil faster / move magnet faster
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Electricity produced in power stations
1) fuel burned to release heat energy 2) heat boils with water to make steam 3) steam drives turbines then generators 4) generators make electricity
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Efficiency equation
electrical energy output /divided by/ fuel energy input x100
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state the 3 greenhouse gases
methane, carbon dioxide & water vapour
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Supports of global warming
more fossil fuels burnt / co2 increasing / average temp of planet increasing
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Refutes of global warming
temp of Earth changes over time / increase in co2 not significant enough / water vapour more significant
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Advantages of off-peak electricity
cheaper / less demand at night / avoids wasting electrical energy
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Disadvantages of off-peak electricity
Inconvenient at night due to noise
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Advantages of fossil fuel
cheap, easy to obtain, doesn't make SO2, flexible in meeting demand
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Disadvantages of fossil fuel
produces co2, spillage+pollution, expensive pipelines needed, causes acid rain
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Nuclear fuel advantages
cost+rate quite low, flexible in meeting demand, doesn't produce greenhouse gases, high stocks, reduces fossil fuels
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Disadvantages of nuclear fuel
very expensive to store, high maintenance costs, long start-up time, dangerously radioactive for thousands of years
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power formula
current x voltage
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total cost formula
no. of kWh used x cost per unit
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energy supplied formula
power x time
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Name 3 types of fuel used in power stations
fossil fuel, biomass & nuclear fuel
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Give example of sources of background radiation
cosmic rays from outer space / radioactive substances in rocks, soil & living things
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People who handle radioactive materials need to take safety precautions... such as...?
wear protective clothing / minimise exposure time / store in shielded containers / keep distance
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Alpha
...is STRONG! // absorbed by a few cm of air or paper
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Beta
...is REASONABLE! // passes through air and paper. Absorbed by a few mm aluminium
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Gamma
...is WEAK! // very penetrating. Needs many cm of lead to metres of concrete to stop it.
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uses of alpha radiation
smoke detectors
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uses of beta radiation
paper thickness gauge
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uses of gamma radiation
cancer treatment / & to sterilise medical equipment
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What is the universe made up of?
galaxies, black holes, stars, planets, comets & meteors
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Why can nothing escape from black holes?
because their gravity is very large
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Problems when dealing with radioactive waste
target for terrorist activity / radioactive for ages / kept outta ground water to avoid contamination
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Problems with manned space travel
Planets very far away so takes years to reach them & also the fuel takes up most of spacecraft
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Once probes arrive on planets, what info can they send back about the planets?
temperature / magnetic field / gravity / atmosphere
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Pros of unmanned space travel
costs lower & safety not a consideration
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Cons of unmanned space travel
instruments must need 0 maintenance & reliability has to be high!
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The distance light travels in a year is called...
a light year
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What does NEO stand for?
Near Earth Object
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Consequences of an asteroid colliding with Earth
heat cause widespread fires, trigger climate change, whole species become extinct, sunlight blocked by dust
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What is a comet?
A small body with core of frozen gas and dust. Have highly elliptical orbits & speed increases as approaches sun
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what does the Big Bang theory state?
the Universe started billions of years ago & universe is expanding
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What is red shift?
The shifting of the wavelengths of light towards the red end of the spectrum
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What can we observe when we look at the stars?
all galaxies moving away / distant galaxies moving more quickly away / microwave radiation received from all universe
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How is a proto-star formed?
When interstellar gas clouds collapse under gravitational attraction
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Then what???
Then thermonuclear fusion reactions happen, releasing massive energy and increasing stars temperature.
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What did Galileo discover?
He used telescopes to observe surface of moon. Discovered that it wasn't perfect sphere. Also 4 moons orbit Jupiter. Venus has phases so couldn't be attached to crystal sphere but it orbited Sun
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Why were Copernicus and Galileo's theories not widely accepted?
Their ideas were in direct opposition to Catholic Church's belief that Earth was centre of universe
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What is speed measured in?
m/s, km/h & mph
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Speed formula
SPEED IS DISTANCE OVER TIME!!
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What do you need to know to work out the acceleration of a moving object?
change in speed & time taken
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What are forces?
pushes or pulls
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What are forces measured in?
Newtons (N)
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What does acceleration of an object depend on?
force applied & mass of object
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The stopping distance of a vehicle depends on...
thinking distance & braking distance
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Thinking distance is increased if...
Vehicle is travelling faster / ill driver or tired / distracted driver
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Braking distance is increased if...
vehicle going faster / poor weather / vehicle in poor condition
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What is kinetic energy?
The energy an object has because of its movement.
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Kinetic energy of an object depends on:
mass and speed
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Modern car safety features
seatbelts, crumple zones, air bags, collapsible steering column
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car safety features for prevention
anti-lock braking systems prevent tyres from skidding // & traction control prevents car from skidding while acceleration
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Stopping forces experienced in a collision can be reduced by:
increasing stopping or collision time OR increasing stopping or collision distance
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Gravitational Potential Energy (GPE) is stored due to...
its position in gravitational field & its mass
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Other cards in this set
Card 2
Front
Heat is a measurement of energy on an.....
Back
Absolute scale (always joules)
Card 3
Front
The amount of energy needed to raise temp of something depends on what 3 things?
Back
Card 4
Front
What is specific heat capacity?
Back
Card 5
Front
What does specific latent heat depend on?
Back
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