Science A (Core): Physics - The Basics Flashcards
How is heat energy (infrared radiation) given out by objects?
All objects emit and absorb heat (hot objects emit more than they absorb and cold objects absorb more than they emit)
What colours absorb and emit more heat than others?
Dark, matt colours are good absorbers and emitters
Light, shiny colours are bad absorbers and emitters
What are the 3 states of matter and how are the particles arranged?
Solids: particles close together and fixed
Liquids: particles quite close but can move around
Gases: particles spread apart and move freely around
What is conduction and where does it occur best in?
Conduction is the transfer of energy by particles vibrating (mainly in solids and especially in metals)
What is convection and where does it occur best in?
Convection is the transfer of energy by particles moving around (in gases and liquids)
What is the difference between evaporation and condensation?
Evaporation is when a liquid changes into a gas
Condensation is when a gas changes into a liquid
What can affect the rate of heat transfer?
Heat transfer is affected by: surface area; material type (conductor / insulator); the temperature difference (a big temperature difference means a faster energy transfer)
How can heat transfer be reduced?
Conduction, convection and radiation can all be reduced
How is heat loss reduced in the home?
Insulation (cavity wall; loft; double glazing etc…)
What is a U-value?
A U-value is a measure of how well heat can pass through a material
High U-value = lots of heat loss
How can insulation save you money?
Payback time = initial cost ÷ annual saving
Payback time is the time it takes to save the amount of money spent on the insulation
What is specific heat capacity?
How much energy something can store (the amount of energy needed to raise 1kg of material by 1oC)
How can you calculate how much energy is stored in a material?
E = m x c x Ѳ
Energy (J) = Mass (kg) x specific heat capacity (J/kgoC) x temperature change (oC)
What is the rule with energy?
Energy cannot be created or destroyed, only transferred
Electrical > light + sound
Chemical > kinetic > gravitational
What is efficiency?
All machines waste energy (usually as heat)
Efficiency is how much energy is transferred usefully
Efficiency = useful energy out ÷ total energy in
What is a sankey diagram and what does it show?
A sankey diagram shows how much energy of the input is changed into different types of energy – the wider the arrow the more energy it shows
How can you work out how much electrical energy is transferred by an appliance
E = P x t
Energy transferred = power of the appliance x time it is used for
What is electricity measured in?
Kilowatt-hours
(kWh)
How is the cost of electricity calculated?
Cost = energy transferred (kWh) x price per kWh
This is often shown on an electricity meter
How is electricity transferred across the UK?
The National Grid
What is a non-renewable energy resource?
An energy resource that will run out one day (e.g. coal, oil, gas and nuclear fuel)
How are energy sources used to generate electricity?
Fuel is burnt / reacted releasing heat which turns water to steam turning turbines and generators which generate the electricity
How does the start-up time for power stations vary?
Gas – quickest
Oil
Coal
Nuclear – longest
What is a renewable energy resource?
An energy resource which will never run out (wind, wave, tide, hydroelectric, solar, biofuel etc…)
What are the benefits and disadvantages of non-renewables?
Fossil fuels are quick and reliable and relatively cheap however they release CO2 as well as oil spills / mining is ugly and dangerous
Nuclear is very reliable but the waste is very dangerous
What are the benefits and disadvantages of renewables?
Renewables will never run out and are generally clean and good for the environment, however they are not reliable (no wind then no turbine / no sun then no solar panel)
What are the good and bad points for biofuels?
Biofuels are carbon neutral however trees still need to be deforested
What is carbon capture and storage?
Carbon dioxide can be ‘caught’ and put into holes in the North Sea where oil and gas used to be (reducing global warming risks)
What are the basic properties of a wave?
Amplitude = energy of wave
Wavelength = length of one full wave
Frequency = number of waves per second (Hz)
What is the difference between a transverse and longitudinal wave?
A transverse wave has vibrations up and down the wave direction
A longitudinal wave has vibrations along the direction of the wave (with compressions and rarefactions)
How can wave speed be calculated?
Wave speed = frequency x wavelength
V = f x λ
What are the laws of reflection?
Angle of incidence = angle of reflection
How does a mirror work?
A virtual image is shown in a mirror
What is diffraction?
The spreading out of a wave
What is refraction?
Waves changing direction (due to different mediums)
What is the electromagnetic spectrum made of?
Gamma rays (high frequency)
X-rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves (low frequency)
*High frequency = short wavelength
What are the different electromagnetic waves used for?
Gamma – cleaning medical equipment
X-rays – medical imaging
Ultraviolet – bank notes authenticity
Visible light – optical fibres
Infrared – remote controls
Microwaves – food cooking / phones
Radio waves – television and radio
*Some waves such as gamma, x-rays and ultraviolet are bad for health
How do we hear?
Sound waves travel and vibrate
What is the pitch of a sound wave?
Higher frequency = higher pitch (a squeaking mouse versus a mooing cow)
What is the Doppler effect and red-shift?
Wavelength and frequency change if the wave source moves
Galaxies are moving away from us and their light is red-shifted
How did the universe begin?
Big bang – the universe is still expanding
