Science A (Core): Physics Flashcards
What are the 3 ways in which energy can travel?
Conduction, convection and radiation
Explain what conduction is
When energy is passed from one particle to another (via vibrations)
What type of materials are good conductors and what type of materials are bad conductors (good insulators)?
Metals are good conductors (e.g. copper) and non-metals are good insulators (e.g. plastics)
Does conduction happen best in solids, liquids or gases?
Explain your answer
Solids – the particles are close together
Explain what convection is
Heat rises because particles gain energy, spreading out and becoming less dense – when they lose energy they become more dense, sinking and forming the convection current
What is a vacuum and which forms of energy movement does it stop (convection / conduction / radiation)
A vacuum is a space with no particles – this prevents energy transfer via conduction and convection (radiation can pass)
Does convection happen best in solids, liquids or gases?
Explain your answer
Convection happens best in liquids and gases as the particles are able to move
How does the outside temperature affect the rate at which heat is transferred?
The greater the temperature difference the greater the heat transfer (loss or gain)
What type of objects usually emits radiation energy?
Hot objects as well as black objects are good emitters of radiation
What type of material absorbs radiation and what type of material reflects radiation?
Black matt materials absorb radiation the most
White shiny materials reflect radiation the most
Which home insulation methods are usually the most cost effective?
Cavity wall insulation
Give 3 examples of how energy can be lost from a house and explain how heat loss can be reduced
Windows – use double glazing / thick curtains
Walls – use cavity wall insulation
Loft – use loft insulation (fibre glass)
What are the 10 types of energy? Explain each one
Electrical; light; sound; kinetic (movement); nuclear; thermal (heat transfer from hot to cold objects); radiant (electromagnetic radiation from hot objects); gravitational potential; elastic potential; and chemical
What 2 things affect the amount of energy an appliance transfers?
Power and length of time the appliance is on
What is power, and what units is it measured in?
Power means “how much energy per second”, measured in watts (W) or kilowatts (kW)
What is the equation for working out power?
Power (W) = Energy (J) ÷ Time (s)
What units is energy measured with?
Joules (J) or kilojoules (kJ)
Draw out the following energy transfers: -
Toaster
Battery operated torch
Skateboarding down a hill
Solar operated fan
Toaster – electrical → thermal
Battery operated torch – chemical → electrical → light (+ thermal)
Skateboarding – gravitational potential → kinetic → thermal (frictional)
Solar operated fan – light → electrical → kinetic
What happens to the energy that is wasted in energy transfers?
It is transferred to the surroundings (usually heating the surroundings up)
What does energy efficiency mean and how is it worked out?
Efficient devices transfer more energy (wasting less)
Efficiency = useful energy output ÷ total energy inpu
How would you make these items more efficient: -
Toaster
Light bulb
Car
Toaster – stop it losing light
Light bulb – stop it losing heat
Car – stop it losing heat and sound
What are the different energy resources?
Solar; tidal; wind; geothermal; hydroelectric; fossil fuels; nuclear; wave
What are the 3 types of fossil fuel?
Coal, oil and natural gas
How can you work out the cost of energy transferred from the mains supply?
Energy transfer = kilowatt hours x cost per unit
What is the difference between renewable and non-renewable energy resources? Give examples of each
Renewable resources can never run out (e.g. wind) whilst non-renewable resources will
Explain how fossil fuel or nuclear power stations work
Fuel is burnt / reacted producing heat, turning water to steam – the steam turns a turbine which turns a generator, producing electricity
What is the job of a turbine?
Turbines are designed to spin a generator
How do generators work (what are they made of)?
Generators have a magnet, which spins within a coil of wire, inducing an electrical charge
Why are fossil fuels bad for the environment?
Fossil fuels release carbon dioxide (CO2), which can lead to global warming (+ sulfur dioxide which leads to acid rain)
What causes acid rain, and why is it an environmental problem?
Sulfur dioxide causes acid rain (which can kill plants and fish etc…)
What causes global warming, and why is this bad for the environment?
Carbon dioxide causes global warming (increases temperature which can cause ice caps to melt resulting in flooding etc…)
How does the national grid utilise step-up and step-down transformers?
Step-up transformers increase the voltage before the electricity goes into the cables – meaning the electricity is carried more efficiently (as there is less heat loss)
Step-down transformers reduce the voltage before the electricity reaches our house (making it safer)
What happens to the current when the voltage is increased – how does this affect heat loss from electrical cables?
Step-up transformer increases the voltage decreases the current (reducing heat loss from the cables)
What are the pros and cons of producing energy using nuclear fuel?
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain; is reliable
Cons – toxic waste and expensive to decommission
What are the pros and cons of producing energy using wind turbines?
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain; is renewable and reliable
Cons – ugly and noisy; unreliable; take up a lot of space
How can geothermal energy be used to generate electricity? What are the pros and cons?
Pipes take water down to hot rocks within the Earth (water is heated, forming steam which turns turbines which spin generators)
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain; is renewable and reliable
Cons – few areas suitable
How can tidal energy be used to generate electricity? What are the pros and cons?
Tides run through turbines (on tidal barrages), which spin generators
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain and is renewable
Cons – affects habitats of wading birds and is unreliable
How can hydroelectric energy be used to generate electricity? What are the pros and cons?
Water falls through turbines, which spin generators
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain; is renewable; reliable and can be stored
Cons – environmentally damaging to area (destroys habitat / ecosystems)
Order the following which generate electricity fastest: coal; oil; gas; and nuclear
Gas
Oil
Coal
Nuclear
How can the Sun be used to generate electricity? What are the pros and cons?
Solar cells use light energy to generate electrical current
Pros – no carbon dioxide or sulfur dioxide so no global warming / acid rain; is renewable
Cons – very expensive and is unreliable
What is the main advantage of using non-renewable resources rather than renewable resources?
Non-renewable energy resources release a lot of energy quickly, and relatively cheaply
How are the particles in a solid arranged?
What movement can occur?
Close together with a regular pattern
Particles are able to vibrate on the spot
How are the particles in a gas arranged?
What movement can occur?
Far apart and random
Particles are able to move quickly in all directions
How are the particles in a liquid arranged?
What movement can occur?
Close together but random
Particles are able to move around one another
Draw out a basic heating curve for water (melting point 0oC and boiling point 100oC)
Draw out a basic cooling curve for salol (melting point 69oC)
Where are metals generally extremely good at conducting both heat and electricity?
Metals have a sea of delocalised electrons – these gain energy when the metal is heated and as they are not attached to any specific atom can move through the metal quickly
What is a Leslie cube?
A Leslie cube is a device which has sides made of different materials – when filled with hot water the energy emitted from each surface will vary
How does a thermos flask work to reduce heat loss (by design)?
A thermos flask reduces heat loss via conduction, convection and radiation
Explain the key principles of a thermos flask and how it works
Glass bottle is double-walled with a vacuum between the two walls
Walls either side of the vacuum are silvered
Bottle is supported by insulating form
Stopper is made of plastic and filled with cork or foam
The whole design minimises any heat loss through conduction, convection or radiation
How does evaporation help when we sweat?
Evaporation helps to cool us down by removing heat from our body to the environment (utilising sweat) – as the sweat evaporates from liquid to gas a small amount of heat is taken from that area of the skin…
Why does condensation occur?
When particles lose enough energy to the surroundings they can change state from a gas to a liquid
How do plants keep themselves cool?
Plants utilise a transpiration stream to keep themselves cool – water is moved from the roots to the surface of the leaves where it evaporates
What is a U-Value?
What does it measure?
A U-Value is a measurement of the effectiveness of the insulation in a home – the lower the U-Value the more effective the insulation
What is payback time?
Payback time is the time it takes to get your money back from investing in insulation
Payback time (years) = cost of insulation (£) ÷ savings per year in fuel costs (£)
What is specific heat capacity and how can it be worked out?
The amount of energy it takes to heat up 1kg of the substance by 1oC – this is the specific heat capacity
What is the equation to work out the energy needed to heat something?
Energy (J) = Mass (kg) x Specific Heat Capacity (c) x Change in Temperature (oC)
Q = mc∆T
What is a Sankey diagram?
Sankey diagrams summarise the energy transfers occurring
What are efficiency ratings?
Efficiency ratings show how much energy an appliance (or house) uses as well as an indication to their running costs
What is a power rating?
Power rating is how much energy a device uses (1 watt = 1 joule per second)
What are generators and how do they work?
Generators are devices which transfer kinetic energy into electrical – they induce a current by spinning a coil of wire within a magnet (or magnet within a coil of wire)
How are generators spun?
Generators are spun via a connecting turbine – this is either spun directly (i.e. from a wind farm) or turned when fossils fuels or nuclear fuel heats water which turns to steam and drives the turbine
What do waves transfer?
(They do this without transferring what?)
Transfer energy without transferring matter
Draw and label this wave: -
Frequency – number of waves produced each second (Hz)
What do all electromagnetic waves have in common?
They all travel at the same speed through a vacuum – the speed of light (300’000’000m/s)
Name the electromagnetic spectrum from shortest to longest wavelength
Gamma (shortest)
X-rays
Ultra-violet
Visible light
Infra red
Microwaves
Radio waves (longest)
What is a longitudinal wave and what does it look like?
Vibrations in the same direction as the wave (e.g. sound)
What can happen when radiation is absorbed by a substance?
Radiation may make things hotter, or set up an alternating current with the same frequency as the radiation itself
What are the effects of these types of electromagnetic radiation on living cells: -
Radio waves & visible light
Microwaves & infrared
X-rays, UV and gamma rays
Radio waves & visible light have very little effect on cells
Microwaves and infrared can cause heating of cells
X-rays, UV and gamma rays can cause ionization of cells and lead to mutations, cancers and death
How can the harmful effects of X-rays be reduced?
Reducing exposure & using lead aprons
How can the harmful effects of UV radiation be reduced?
Reduce exposure to the Sun (using a broad spectrum sun screen)
How are these electromagnetic waves used: -
Radio waves
Microwaves
Radio waves: communications
Microwaves: heating food & sending information (e.g. mobile phones)
How are these electromagnetic waves used: -
Infrared
Visible light
Infrared: communications (phone & via optical fibres), remote controls and electric heaters
Visible light: used to send information via optical fibres
How are these electromagnetic waves used: -
Ultra-violet
X-rays
UV: security tags and sun-beds
X-rays: imaging the body (broken bones)
How are gamma rays used?
Sterilising surgical equipment by killing bacteria & radiotherapy for cancer patients
Which 4 forms of electromagnetic radiation can be used for communications?
Communications via: radio waves, microwaves, infrared waves (optical fibres) and visible light (optical fibres)
Why are microwaves used to communicate with satellites?
Microwaves are able to pass through the Earth’s atmosphere to reach the distant satellites
What is a transverse wave and what does it look like?
Vibrations which are sideways (e.g. light)
What are rarefactions and compressions?
Regions where the wave is pulled apart (rarefactions) and pushed together (compressions)
What is the formula for calculating the speed of a wave (triangle will also help)
Speed (m/s) = Frequency (Hz) x Wavelength (m)
What properties effect waves?
Waves can be reflected, refracted and diffracted
How can light be reflected?
Light can reflect off an even surface (clear) or from an uneven surface (diffuse)
What is refraction?
Refraction occurs as light can bend at the boundary between materials of different densities
Draw out an angle of incidence and an angle of reflection
Angle of incidence = angle of reflection
How can the refractive index be worked out?
Refractive index = sin i ÷ sin r
What is constructive interference?
Where two waves arrive in step reinforcing one another (increasing the amplitude)
What happens if the size of a gap is made similar to the wavelength of a wave?
Diffraction increases
What is destructive interference?
Where two waves arrive out of step cancelling one another out
What happens to diffraction if the wavelength is increased?
Diffraction increases
What does this picture show?
Reflection
What does this picture show?
Refraction
What does this picture show?
Refraction
What does this picture show?
Diffraction
What does the red-shift provide evidence for?
The big bang – galaxies are moving away from us, providing evidence that the universe is still expanding after the explosion of the big bang
How do optic fibres work, and what are they used for?
Optic fibres carry information (light / infra red) via total internal reflection (used for networking / endoscopes)
How do people who work with radiation monitor their exposure?
Photo film badges, half covered with paper and half covered with foil – the film turns black if radiation hits it (top half = beta, all = gamma)
What is red-shift?
When light rays moving away from us appear red, as the wavelength becomes stretched
What is cosmic microwave background radiation?
The relatively uniform background radiation is the remains of energy created just after the Big Bang
What is amplitude?
A measure of how loud a sound is (how much energy is carried)
What is pitch?
Pitch is how high or low a sound is, dependent upon the frequency of the waves
What properties does an image in a plane mirror have?
Image is the same size, it is as far behind the mirror as the object is in front, and it is formed from diverging rays meaning it is virtual
Draw an image as shown in a plane mirror
Plane mirror image
What type of EM radiation can we detect?
Visible light
What colour of light is refracted the most and why?
Violet (it has the shortest wavelength)
