P8 - Global challenges Flashcards
What three things can happen when a wave hits a boundary?
1) Transmission: It goes through
Refraction is a special from of transmission when the wave bends when going through
2) Absorption: The boundary absorbs the wave
Once a wave is absorbed it can be remitted
3) Reflection: Wave bounces off at an angle
What happens when wave hits white / shiny object?
What happens when wave hits transparent object?
What happens when wave hits black object?
White or shiny :Light is reflected
Transparent: Light is transmitted
Black: Light is absorbed
What is a ‘perfect black body’?
It is a perfect absorber (all light is absorbed) and a perfect emitter (all light is emitted)
What is blackbody radiation?
Radiation emitted from an object depending on how hot it is
What two things does increasing temperature cause
- Wavelength is decreased (as a result frequency is increased)
- More light is emitted (light intensity increases)
How does an object’s temperature change in terms of radiation?
- If object warmer than surrounding, radiation is emitted and object temperature decreases
- If object cooler than environment, radiation is absorbed and the object temperature increases
Difference between speed and velocity?
Difference between Distance and Displacement?
VECTORS: Velocity, Displacements
SCALARS: Speed, Distance
What is displacement?
Distance in a straight line from an objects starting point
Eg: if a person runs a 150Km lap
Distance covered = 150Km
Displacement covered = 0Km as they returned to the same starting point `
Equation for speed and velocity:
Speed = distance / time
Velocity = displacement / time
How do you convert
m/s -> Km/h?
Km/h -> m/s?
m/s -> divide 1000 -> km/s -> times 3600 -> km/h
km/h -> times 1000 -> m/h -> divide 3600 -> m/s
What is the thinking distance?
The distance travelled from you seeing the risk to when you press the brakes
What is the braking distance?
The distance travelled from pressing the brakes until the car stops
What is the stopping distance?
The total distance for the vehicle to stop.
Stopping distance = thinking distance + braking distance
Relationship between speed and thinking distance:
Thinking distance is directly proportional to speed
EG is speed doubles, the thinking distance doubles
Relationship between speed and braking distance:
Braking distance is directly proportional to speed squared
If speed triples, the braking distance times by 9
What is reaction time?
The time taken for the driver to notice the hazard
10 types of energy?
- Light energy
- Sound energy
- Thermal energy : Any object - the hotter the more energy it has
- Chemical: anything that can release energy by chemical reaction
- Elastic potential energy: anything stretched
- Gravitational potential energy: anything in a gravitational field
- Kinetic energy: Anything moving
- Magnetic energy: when magnetic objects repel or attract
- Nuclear energy: atomic nuclei release energy from this stores in nuclear reaction
- Electrostatic: When charged objects repel or attract
8 types of energy resources?
- Solar: using the suns energy to produce electricity
-Biomass/ biofuel: Burnt to produce electricity like fossil fuels - Tidal: using tides to turn turbines and produce electricity
- Wind: using winds kinetic energy into electrical energy
- Geothermal: energy derived from the earths thermal
energy - Hydroelectric: Using dams to produce electricity
- Nuclear: using nuclear fission to electricity
- Fossil fuels - combustion of natural gas, coal and oil to produce electricity
How is tides used to produce energy?
1) Tidal barrages are big dams built across rivers with turbines in them
2) When tide comes in the water is let through turbines at a set speed
3) A generator, converts the moving turbine energy into electrical
How is hydroelectrical methods used to produce electricity?
1) Water is stored by building a dam in a valley
2) Water is allowed to flow through dam turning turbines
3) A generator, converts the moving turbine energy into electrical
How does wind produce electricity?
1) Wind turns blades on a wind turbine
2) This kinetic energy is used by generator to turn into electrical energy
How does power stations produce electricity?
1) Fossil fields are burned in a furnace boiler converting the chemical energy into thermal energy
2) This heats up water, boiling it to form steam
3) The high pressure of the steam turns turbines which turns the generator (causing a coil to rotate in a magnetic field generating current)
4) The energy is converted to electrical energy
5) The steam is condensed back into water to be reused again in the boiler.
How does nuclear power stations produce electricity?
IN THE REACTOR CORE
1) Fissionable atoms like Uranium -235 are present and once one neutron is absorbed a chain reaction occurs
2) Moderator: is water and it keeps fission occurring as the 3 neutron emitted in each fission reaction have a lot of energy (they are too fast) therefore the neutrons collide with the H20 molecules slowing them down allowing fission to occur
3) Control rods: they allow us to control number of fission reactions occurring (if control rods lowered they stop neutrons from reach other nuclei slowing it down and vice versa for raising control rods)
IN THE HEAT EXCHANGER
1) The hot water (from energy from fission in reactor core) runs in tube through container of water in heat exchange
2) This transfers energy to the water in heat exchange producing steam as it boils
3) The steam travels up pipe and spins a turbine converting heat energy into electrical energy
IN THE PUMP
1) Pump helps supply heat exchange with constant supply of water as the water in heat exchanger changes state to steam
Advantages / Disadvantages of electricity producing methods:
- Solar
- Biomass/ biofuel
- Tides
- Wind
- Hydroelectric
- Nuclear
- Fossil fuels
Solar:
ADV: No pollution
DIS: Unreliable in cloudy countries or at night
Biofuel:
ADV: Reliable as the crops grow fairly quickly
DIS: Very high cost to produce
Tides:
ADV: No pollution
DIS: Can spoil view and alter habitat for wildlife
Winds:
ADV: No pollution
DIS: Spoil view and is very noisy
Hydroelectric:
ADV: Immediate response to electricity demand as more water can be let out
DIS: Can cause flooding and destroy habitats
Nuclear:
ADV: Less carbon emission
DIS: Dangerous due to exposure to radiation can be cancerous
Fossil fuels:
ADV: reliable
DIS: damaging to the environment, produce carbon causing global warming
Conditions for fossil fuels to be formed?
- An anaerobic environment
- High temperatures
- High pressure
Steps to fossil fuels formation?
1) Plant and animals die and sink to bottom of sea
2) Plant and animal layer gets covered with sediment overtime
3) The sediment creates pressure and higher temperatures, compressing the dead plant and animal material into fossil fuels
4) Coal stays where it is formed as it is a solid while oil moves through porous rocks and eventually forms a reservoir
Disadvantages of fossil fuel usage?
- Contributes to greenhouse effect / global warming
- Non- renewable source
- Produces acid rain:
Sulphur dioxide = Burning oil and coal
Sulphur dioxide + water -> Sulphuric acid
Nitrogen oxide = Burning petrol in cars
Nitrogen oxide + water -> Nitric acid
Carbon dioxide = Burning fossil fuels and deforestation
Carbon dioxide +water -> Carbonic acid
Mains voltage and frequency of AC current in the UK?
Mains voltage: 230V
Frequency: 50Hz (number of times ac current switches direction a second)
Why is copper used in wires?
Why is plastic used as a coat for wire?
Copper in wire:
- conducts electricity
- ductile (moldable)
- High melting points
Plastic for coats:
- Doesn’t conduct electricity - an insulator
3 different wires in plugs:
- their colour
- their function
- position in plug
The live wire
COLOUR: Brown
FUNCTION: Carries high voltage to device
POSITION: Bottom right
The neutral wire:
COLOUR: Blue
FUNCTION: Completes the circuit
POSITION: Bottom left
The earth wire:
COLOUR: Yellow and green
FUNCTION: Safety wire
POSITION: Top
Direction of current flow in plugs?
- The electricity goes through the live wire at 230v
- The current flows through fuse to devices where energy is supplied
- The current flows back through neutral at 0V - all the energy has been supplied to device
4 safety devices:
1) Fuse
2) Circuit breaker
3) Earth wire
4) Double insulation
How does fuses work?
Symbol: a rectangle with a line through it - SEARCH IT
if current is too high, the thin wire in the fuse melts - due to high temperature - and the circuit breaks so current is stopped flowing
How does circuit breaker work?
DRAW DIAGRAM
1) When high amounts of current flows through the live wire - coiled around a magnet - a magnetic field is induced
2) The contacts - which are originally touching - separate as one contact is attracted to the magnetic field.
3) Current is stopped from flowing
How does the earth wire work?
- Earthing is used to protect you from an electric shock.
- It does this by providing an alternate path for a fault current to flow to earth. (EARTHING)
- It also prevent current continuing to flow through the circuit
1) Earth wire has a low resistance
2) If casing of device gets charged, a very high current can flow through earth wire
3) the current goes through the live wire and fuse as well
4) the fuse melts and current stops flowing due to incomplete circuit
How does double insulation work?
Symbol: a smaller rectangle in a larger rectangle - SEARCH IT
- It makes sure there are no metal parts outside as device is double insulated in plastic - insulator
- Double insulation appliances don’t need earth wire as they cannot become ‘live’ - the casing cannot become charges as it is made of plastic
What is the Doppler effect?
1) When an object - emitting waves (Eg. sound waves like from an ambulance truck or light waves from a star) - moves towards an observer (person or object it is moving toward) they receive high frequency waves
- This is because the light, sound or other waves are more compressed so the observer receives more waves per second (higher frequency)
2) When an object is moving away from an observer, they recieve less waves per second (lower frequency).
The Doppler effect and sound?
1) When an object which is producing sound waves, is travelling towards the observer, they hear a higher pitch sound - they recieve more waves per second due to sound waves closer together
2) When an object which is producing sound waves, is travelling away from an observer, they hear a lower pitch sound - they receive less waves per second due to sound waves further apart
What effect does changing frequency and amplitude of sound waves affect the noise?
Changing frequency: changes pitch of sound
- Increased frequency = higher pitch
- Decreased frequency = lower pitch
Changing amplitude: changing volume of sound
- Increased amplitude = louder
- Decreased amplitude = Quieter
The Doppler effect and light?
1) When an object - emitting visible light waves - moves towards the observer, they see a higher frequency colour (towards blue - Blue shifted on the visible light spectrum)
2) When an object - emitting visible light waves - moves away from an observer, they see a lower frequency colour (towards red - Red shifted on the visible light spectrum)
How does the Doppler effect support the Big Bang theory?
- All stars are made of the same chemicals therefore on a absorption spectrum the black lines of all stars should be in the same places
- However, the black lines from stars in the universe are red-shifted (towards red)
- Therefore, we know that the stars are moving away and we are receiving lower frequency colours - less waves per second.
What radiation do all objects emit?
-Infrared radiation
The hotter the object the more IR in a given time
