Physics Unit 1 Flashcards
Describe the process of condensation
When a gas cools, the particles in the gas slow down and lose kinetic energy meaning the attractive forces between the particles pull them closer together
Describe the “cooling effect” of evaporation
The fastest particles with the most kinetic energy are most likely to evaporate and when they do, the average kinetic energy of the remaining particles decreases meaning that the remaining liquid cools
Describe evaporation
If particles are travelling in the right direction and are travelling fast enough to overcome the attractive forces of other particles in the liquid, these particles near the surface of the liquid can escape and become gas particles
Give 4 things that would increase the rate of evaporation and explain why
Higher temperature (more particles have enough energy to escape)
Lower density (forces between particles are weaker so it easier for particles to escape)
Larger surface area (more particles close to surface so that they can escape)
Airflow over the liquid is greater (the lower the concentration of an evaporating substance already in the air it’s evaporating into, the higher the rate of evaporation, a larger airflow means the air around the liquid is replaced more quickly)
What is condensation?
When a gas turns to a liquid
What is evaporation?
When a liquid turns to a gas
Give 4 things that would increase the rate of condensation
Temperature of the gas is lower (average particle energy is lower)
Airflow is less (the concentration of the substance in the air is higher so the rate of condensation is higher)
Temperature of the surface the gas touches is lower
Density is higher (attractive forces between particles is higher)
What is the National Grid?
The system over the whole UK that transports electricity from where it’s produced to where it is needed
How do we increase the voltage of the electricity in the National Grid cables?
We use a step-up transformer that increases the voltage to 400000V and decreases the current
What are the 2 ways that the increasing demand for electricity could be dealt with?
Energy demands of consumers decrease (could be done by increasing energy efficiency)
Energy supplied to National Grid increased
Give 4 reasons that overhead cables would be chosen instead of underground ones
Low set up cost
Easy to access if there are faults
Easy to set up
Minimal disturbance to land
How is the voltage of the electricity decreased for use in homes?
A step-down transformer decreases the voltage and increases the current
What are the 2 types of National Grid cable?
Overhead cables (with pylons)
Underground cables
Why is the voltage so high in the National Grid cables?
To lower the current
Why does the current in the National Grid cables have to be so low?
A high current would mean that most of the energy is lost through heat in the cables
Give 4 reasons that underground cables would be chosen instead of overhead ones
Minimal maintenance needed
Hidden (don’t look ugly)
Not affected by weather
More reliable than overhead cables
What are the voltage in the National Grid cables?
400000V
What are the 4 disadvantages of solar cells?
Don’t generate electricity at night time
Initial costs are high
Too expensive to connect to National Grid
Not visually appealing
What are the 6 advantages of solar cells?
Can be very small for use in handheld devices
Can be used in remote places
No pollution
Very reliable in the summer
Running costs are very small
Can generate electricity for homes
What are the 4 problems with non-renewable energy methods?
Most release carbon dioxide adding to the greenhouse effect
Burning coal and oil releases sulphur dioxide which causes acid rain
Coal mining scars the landscape
Oil spillages can cause serious problems in mammals and birds that live around the sea
What are the 6 factors that are considered when setting up a power station? (Give explanation for each)
Set-up costs (renewable power stations usually cost more to set up than non-renewable)
Set-up time (nuclear take longest, gas are quickest, sometimes discussions can go on for years)
Reliability (non-renewable are always reliable, renewable usually relies on weather)
Running and fuel costs (renewable have lowest running cost because there is no fuel)
Environmental issues (atmospheric pollution, visual, nuclear can have big problems, resources like oil, noise, habitats)
Location (needs to be located near the source of energy, nuclear needs to be away from people and near water for cooling)
What are the 3 disadvantages of nuclear reactors?
Take a long time to set up
All costs are high
There is a possibility of nuclear disasters
What are the 3 advantages of nuclear power?
Produces a lot of electricity
No pollution
Nuclear fuel is fairly cheap
What are the 3 disadvantages of biofuels?
We still don’t know the full impact of biofuels on the environment
Large areas of forest have been destroyed to get to biofuels (loss of habitats, greenhouse effect)
Their use is limited to the amount of farmland that can dedicated to their production
How do solar cells work?
The solar cell is joined in series to some electrical components so that when light hits the solar cell, an electric current is produced
How does hydroelectric power work?
Water is stored in a dam and then all released so that it spins turbines so that electricity can be generated
How do biofuels produce energy?
The same way as fossil fuels
How does wind power work?
Wind spins large turbines which spin generators giving us electrical energy
What are the 3 advantages of tidal power?
No pollution
Reliable because they give us energy twice a day
Minimal running costs
How does geothermal power work?
Cold water is pumped underground where it is heated by hotrocks and pumped back up
The heat causes the water to become steam that drives a turbine
What is carbon capture and how does it work?
It is way of reducing carbon dioxide that leaves power stations
It is done by collecting the carbon dioxide before it leaves the power station and putting it into empty gas fields and oil fields under the sea
How does tidal power work?
The tide comes in and rises up to a pipe which it travels down and spins a turbine and is let out on the other side
The same happens when the tide goes out
What are the 4 types of non-renewable energy sources?
Coal, oil, natural gas and nuclear fuels (uranium and plutonium)
What are the 2 disadvantages of geothermal power?
Not many suitable locations
Expensive to set up (excavation included)
What are the 8 types of renewable energy sources?
Wind, waves, tidal, hydroelectric, solar, geothermal, food, biofuels
What are the 3 advantages of wave power?
No pollution
Low running costs
Don’t look particularly ugly
What are the 3 advantages of hydroelectric power?
No pollution because only rain water is used
Can provide immediate response to energy demand
Problems with reliability are rare (only in droughts)
What are the 3 advantages of energy from biofuels?
Can power some cars
Fuels can be solids, liquids or gases
They are produced using very eco-friendly methods
What are the 4 disadvantages of wind power?
They spoil the view (1500 turbines needed to replace power station)
Can be very noisy
No power when the wind stops
Initial costs are quite high
What are the 4 advantages of wind power?
Renewable
Electricity generated inside the turbine
No pollution
No permanent damaging to landscape because you can remove them and there will be no scarring
What are the 3 disadvantages of wave power?
You need a lot to produce enough energy
Hazard to boats
Unreliable because they depend on waves
What are nuclear power stations?
Where nuclear fission of uranium or plutonium produces the heat to make steam to drive a turbine
How does wave power work?
When a wave moves in, it goes into a pipe and forces air out of the pipe and into a turbine
What are the 3 disadvantages of hydroelectric power?
Requires flooding a valley
Loss of animal habitats
Initial costs are high
What are the 3 disadvantages of tidal power?
Prevents free boat access
Spoils the view
Altering habitats of wildlife
Describe how fuel power stations work
The fossil fuel is burned to convert its stored chemical energy to heat
The heat turns water to steam
The steam spins a turbine generating kinetic energy
The turbine spins a generator which generates electrical energy
What are the 3 advantages of geothermal power?
No environmental problems
Can heat builings directly
Very reliable (consistent)
How does pumped storage work?
At night, the spare energy is used to pump water back up to the top so that it can be released when their is high energy demand
What is the conservation of energy principle?
Energy can’t be created and destroyed but only transferred
What are the 2 formulas for calculating the cost of electricity?
Number of units used (kWh) = power (kW) * time (h)
Cost = no. of units * price per unit
What does “dissapated” mean?
When wasted energy (usually heat) becomes less concentrated (e.g. if heat spreads out)
What is a Sankey diagram?
A diagram that shows the input and output energies of a device and the device’s efficiency
Describe how you would draw a Sankey diagram
Show the energy in going to the left with the number of joules labelled
The energy wasted in different ways are boxes that go downwards and end with a point, label the type of energy and amount (the box widths are proportional to the input energy) (different boxes for different types of energy)
The energy still travelling to the left ends in a point and it is labelled “useful” and then the type of energy and also the amount of energy
Give 4 ways that access to electricity affects standard of living
Many types of energy in the home are convenient and can increase safety (eg. lights)
Refrigerators keep food fresh and keep vaccines cold. Without this, the area’s population can be drastically effected
Electricity is needed in hospitals (X-rays, diagnosis etc.)
Communications require electricity
What is a kWh?
The amount of energy used by a 1kW appliance left on for 1 hour
What is the main cause of inefficiency of devices?
Energy is wasted as heat
What are heat exchangers?
A device that reduces the amount of heat energy lost by collecting some of it back
What is potential energy?
Stored energy that is not being currently used
What are the 3 things you need to consider when buying an appliance?
Cost-effectiveness
Energy-efficiency
Whether the energy type needed is readily available
What is the formula that relates energy, time and power?
Energy = power * time
E = Pt
Describe how heat exchangers work
A cool fluid is pumped through the escaping heat
The fluid temperature increases and can be used for heating
What is the unit for energy used in homes?
Kilowatt-hours or kWh
What are the nine types of energy?
Electrical (flowing current)
Light
Sound
Kinetic (movement)
Nuclear potential (stored in nuclei of radioactive isotopes)
Thermal / heat
Gravitation potential
Elastic potential
Chemical potential (food, fuels etc.)
How do you calculate the power efficiency of a device?
Efficiency = useful power out / total power in
How do you calculate the energy efficiency of a device?
Efficiency = useful energy out / total energy in
What device is usually 100% efficient?
Electric heaters (heat is not waste energy)
What other liquid can be used in heaters and why is it used?
Oil because it has a high boiling point so you don’t have to worry about it evaporating at higher temperatures
How do electric storage heaters work?
They store the heat in concrete or bricks because they have a high specific heat capacity
What appliance needs a high specific heat capacity and why?
Materials used in heaters need a high specific heat capacity so that they can store large amounts of heat energy
What is the specific heat capacity of water?
4200 Joules per kg per degrees C
Why is water used for central heating systems?
High specific heat capacity to store heat
Liquid that can be pumped around a house easily
What are electric storage heaters?
Heaters that store heat energy at night (electricity cheaper) and release it during the day
How much energy is needed to heat 2kg of water from 10 degrees to 100 degrees C?
100 - 10 = 90
Energy = 2 * 4200 * 90
Energy = 756000J
What is the formula for specific heat capacity?
E = mc(theta)
Energy transferred = mass * specific heat capacity * temperature change
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1kg of a substance by 1 degrees C
Why is water preferable to oil in heaters?
Water has a much higher specific heat capacity
What is U-value of a material?
A value that shows how fast heat can transfer through a material
The better the insulator, the lower the U-value
What is payback time?
The amount of time that it takes for the amount of money saved to equal the cost of the insulation
What is the unit of U-value?
Watts per square metre kelvin (W/m^2K)
Describe the 5 methods of home insulation
Draught proofing - strips of foam and plastic around doors and windows that stop heat loss by convection
Loft insulation - a thick layer of fibreglass wool laid out across the loft floor and ceiling reducing heat loss by conduction and convection
Cavity wall insulation - foam squirted into the gap between the bricks reduces convection, conduction and radiation through the gap
Thick curtains - create an air gap between the window and room stopping hot air reaching the glass by convection. Conduction is also reduced
Hot water tank jacket - fibreglass wool around hot water tanks reducing conduction and convection
What is a “cost-effective” method of insulation?
One that has a short payback time
How do you calculate payback time?
Payback time (years) = initial cost / annual saving
What is an “effective” method of insulation?
One that gives you a large annual saving (they save you a lot of money each year)
Describe the arrangement, forces and energy in solids
Strong forces of attraction hold the particles in a fixed regular arrangement
The particles don’t have much energy so that can only vibrate about their fixed positions
How does the surface type of the object affect its radiation?
Dark, matte surfaces absorb and emit much more infrared radiation than shiny, light surfaces
Describe the convection in an immersion heater
Heat is transferred from the heater coils to the water by conduction (particle collisions)
The particles near the coils get more energy so they move around faster meaning there is more distance between them meaning that this water becomes less dense
The hotter water rises because it is less dense and displaced the colder water out of the way towards the heater coils
The cold water is heated by the coils and the hot water cools at the top of the immersion heater
This circuit repeats over and over again
What factor affects the rate of conduction?
If the particles are closer together, the particles will collide more often and the rate of conduction will be higher
Which states of matter does convection occur in?
Liquids and gases
What is convection?
The process where more energetic particles move from the hotter region to the cooler region and take their heat energy with them
Why don’t shiny, light surfaces absorb as much infrared radiation?
They reflect off most of the waves
What is the simplest way that animals have evolved to deal with heat transfer?
Arctic foxes have small ears to prevent heat loss by radiation
Desert foxes have large ears that allow them to easily lose heat to keep them cool
What are the 3 ways that heat energy can be transferred?
Radiation, conduction and convection
How does temperature difference affect transfer of energy by heating?
The larger the temperature difference between a body and its surroundings, the faster energy is transferred by heating
How does surface area affect the rate of heat energy transfer?
Heat is radiated from the surface of an object so the larger the surface area, the more infrared waves can be emitted from the object
Describe the arrangement, forces and energy in gases
Almost no forces of attraction
Particles have more energy than in liquids and solids and are free to move in random directions at high speeds
What is conduction?
The process where vibrating particles pass on their extra kinetic energy to neighbouring particles
This causes heat to spread throughout a solid
How does surface area affect infrared radiation?
The larger the surface area, the higher the rate of infrared radiation because there are more places that the waves are emitted from
What is kinetic theory?
The theory that describes how particles move in solids, liquids and gases and tells us that the energy of a particle is its movement or vibration (kinetic energy)
In terms of heat radiation, what happens when an object is hotter than its surroundings?
The object emits more radiation than it absorbes as it cools
How does volume affect rate of heat energy transfer?
If 2 objects at the same temperature have the same surface area but different volumes, the object with the smaller volume will cool quicker
This is because a higher proportion of the object will be in contact with its surroundings
In terms of heat radiation, what happens when the object is cooler than its surroundings?
It absorbs more radiation than it emits as it warms up
What causes metals to be good conductors?
Their free electrons can easily collide with each other and pass on the kinetic energy
What is a convection current?
The way that, in convection, the hot water rises becomes cold and sinks and heats again and this circuits repeats again and again
Which states of matter does conduction occur in?
Solids
Describe the arrangement, forces and energy in liquids
The forces of attraction are weaker so the particles are still close together but they can move past each other
The particles have more energy than in a solid so they move in random directions at low speeds
Describe how solar hot water panels make use of our knowledge of surface types and radiation
They contains water pipes under a black surface to heat the water in the pipes
Radiation from the Sun is absorbed by the black surface to heat the water in the pipes
What happens to the particles of an object when you heat it?
The particles get more kinetic energy and vibrate or move faster
How does the type of material affect the rate of heat energy transfer?
Conductors transfer heat much faster than insulators
If an object is in contact with a conductor, the heat will be conducted away much faster than if the object was in contact with an insulator
What is heat radiation?
The transfer of heat energy by infrared radiation
What makes a material an insulator?
When the material has larger spaces between its particles
How do vaccum flasks prevent heat transfer?
The glass bottle is double-walled with a vaccum between the 2 walls preventing all conduction and convectiom through the sides
The bottle is supported with insulating foam minimising conduction to or from the outer glass bottle
The stopper is made of plastic and filled with cork or foam to reduce heat conduction
What is the law of reflection?
Angle of incidence = angle of reflection
What is the formula that links wavelength and frequency?
Wave speed (m/s) = frequency * wavelength
What is the angle of reflection?
The angle between the reflected light ray and the normal
What is wavelength?
The length of a full cycle of the wave (eg. from crest to crest) in metres
Why can we see objects?
Because different light rays reflect off different objects and go into our retina
Which types of wave are transverse?
All EM waves
Water ripples
What is the angle of incidence?
The angle between the normal (imaginary line perpendicular to the surface) and the incident ray (the light ray approaching the mirror)
How is a diffraction diagram drawn?
Lots of parallel vertical lines on the left side of the gap and lots of curved, spread out waves on the right
What 2 factors affect the amount of diffraction?
The narrower the gap, the more the wave spreads out
The longer the wavelength, the more the wave spreads out
Describe a diagram of refraction
The incident ray hits a glass block (or other more dense medium) and the ray bends towards the normal and is called the refracted ray
When the refracted ray emerges from the fender medium, it travels away at the same angle as the angle of incidence and is called the emergent ray
What is a longitudinal wave?
A wave where the vibrations are parallel to the direction of energy transfer of the wave
What does maximum diffraction look like?
The emerging waves look like semi-circles
What causes refraction?
When the wave suddenly changed to a medium that has a different density, it changes speed accordingly and this changes the direction of the wave
Describe how you draw a ray diagram for an image reflected in a mirror
Draw the reflected image on the other side of the mirror to the actual object (exactly as far away)
Draw an eye looking at the mirror from an angle
Draw the reflected ray coming from the virtual object to the top of the eye with an arrow on the ray to show this (dotted line for the virtual side of the mirror)
Draw the incident ray coming from the real object to the point where the reflected ray and mirror meet (add an arrow on the ray to show this)
Do the last 2 steps again but where the reflected ray meets the bottom of the eye
Which types of waves are longitudinal?
Sound waves and ultrasound
Shock waves
What happens when a wave hits the boundary at an angle?
The wave bends towards the normal
What is refraction?
When a wave crosses the boundary between 2 substances, it changes direction
What 4 things is the reflected image and why?
Same size as the object (it is as far behind the mirror as the object is in front)
Virtual (appears to be behind the mirror)
Upright
Laterally inverted (the left and right sides are swapped)
What is frequency?
The number of complete waves passing a certain point every second measured in Hz (s^-1)
What are the 3 ways that the direction of travel of a wave can be changed?
Reflection
Refraction
Diffraction
What is transverse wave?
A wave where the vibrations are perpendicular to the direction of energy transfer of the wave
What is amplitude?
The displacement of the wave from the rest (middle) to the crest (top) in metres
What happens if the wave hits a boundary face on?
No refraction occurs
What is diffraction?
If the wavelength of a wave is longer than the size of a gap that it has to go through, the wave will spread out when it emerges from the gap
How does changing the surface affect the reflection of light rays off it?
An uneven surface causes light to reflect off in all directions so we can’t see a clear reflection
A smooth and shiny surface reflects all of the light rays in one direction meaning that we can see the reflected image
What are the 2 types of waves?
Longitudinal
Transverse
Describe how a camera works
Use a lens to focus visible light onto a light sensitive film or electronic sensor
The lens aperture controls how much light enters the camera (like a pupil)
The shutter speed determines how long the film or sensor is exposed to light
Varying the shutter speed and aperture can decide how much light is in a photo
How are short radio waves sent to their destination?
You have be in a line of sight of the transmitter to receive the very short radio waves
What are all the wave types in the electromagnetic spectrum in order? Give their wavelengths
Radio (1m to 10^4m)
Microwaves (10^-2m)
Infrared (10^-5m)
Visible light (10^-7m)
Ultraviolet (10^-8m)
X-rays (10^-10m)
Gamma rays (10^-12m)
How are long radio waves sent to their destination?
They can diffract around hills and other similar obstacles so you don’t need a direct line of sight
How do remote sensing satellites work?
Microwaves are used by the satellites to see through the clouds in order to monitor oil spills, icebergs etc.
Describe how a satellite TV or mobile phone signal would travel to its destination
The transmitter would transmit the signal into space where it would be picked up by a satellite
The satellite would then transmit the signal to the TV or mobile phone
Which type of wave is used for FM radio and TV?
The very short wavelength radio waves
Why are people worried about how taking mobile phone calls could be dangerous to us?
If microwaves are travelling somewhere and they go through some water, the water would absorb them and then be heated up
If we hold a mobile phone close to our head while taking a call, the microwaves could be cooking the water in our cells and possibly damaging us
How are medium-length radio waves sent to their destination?
They bounce off the ionosphere (electrically charged layer of the atmosphere) to get to their destination
In communication, what are microwaves used for?
Satellite communication and mobile phones
Give 2 ways in which infrared waves are used for communication
Sent by remote controllers in patterns to give instructions
IR and visible light are used to carry data over optical fibers by bouncing off the sides of the fibre
What is the electromagnetic spectrum?
The continuous group of wave types that are all transverse and travel at the speed of light
Decreasing the wavelength would bring you up in the electromagnetic spectrum
Why are microwaves used for satellite communication instead of radio waves?
The wavelength has to be short enough to pass through the Earth’s watery atmosphere to get to the satellites
What are radio waves used for?
Communication including TV and FM radio transmissions
What causes red-shift?
The doppler effect
What is cosmic microwave background radiation?
Low frequency electromagnetic radiation coming from all parts of the universe
What causes sound waves?
Vibrating objects
Why is the big bang theory accepted over the steady state theory?
It is the only theory that explains the cosmic microwave background radiation
How does big band theory explain the cosmic microwave background radiation?
Just after the big bang the universe was very hot so everything in the universe emitted high frequency radiation
As the universe expanded it cooled so the radiation dropped in frequency to microwaves
Describe the steady state theory
The universe has always existed as it does now and always will do
The universe is expanding because matter is being created in the spaces as the universe expands
What effect does changing the distance to a galaxy have in red-shift and why?
The further away the galaxy, the greater the red-shift because galaxies further away are moving away from us faster than nearer ones
Describe the doppler effect
The frequency of a source moving towards you will seem higher so the wavelength will seem shorter
The opposite is true for an object moving away from you
What type of wave does the doppler effect occur in?
Both transverse and longitudinal
Describe red-shift
Different chemicals absorb different frequencies of light so each element produces a specific set of dark lines at the frequencies that it absorbs in the visible spectrum
The dark lines in light from distant galaxies are shifted towards the red side of the spectrum
This is red-shift
How do we know that the universe is expanding?
The light from other galaxies is red-shifted
What are the 2 problems with the big bang theory?
There are observations the theory can’t explain (universe’s expansion is increasing when it should be slowing)
No explanation for what caused the explosion
Which type of wave is sound?
Longitudinal
Describe the big bang theory
All matter and energy in the universe must have been compressed into a very small space and then it exploded from that point and started expanding
What effect does changing the frequency of a sound wave?
The higher the frequency, the higher the pitch
What effect does changing the amplitude of a sound wave have?
The higher the amplitude, the louder the sound
How is the universe changing?
It is expanding and all galaxies are moving away from each other
What are the 2 theories for the origin of the universe?
Big bang theory
Steady state theory
Which states of matter does sound travel through the fastest and slowest?
Faster in solids than liquids
Faster in liquids than gases
What else can sound waves do?
Diffract and refract
Why do echoes happen?
They are reflected sound waves
