Physics

Created by

Grace Tanner

Cards (99)

Energy Stores 
1) Elastic potential
2) Gravitational potential
3) Thermal
4) Electrostatic
5) Nuclear
6) Chemical
7) Kinetic
8) Magnetic
9) Light
10) Sound
How is energy transferred? 
1) Mechanically - force doing work
2) Electrically - work done by moving charges
3) Heating/Radiation - light, sound
How can work be done?
When a current flows or by a force moving an object
Kinetic energy formula 
E=1/2mv²
Kinetic energy(J) = 0.5 x mass(kg) x speed²(m/s)
Gravitational potential energy formula 
E=mgh
G.P.E(J) = mass(kg) x gravitational field strength (N/kg) x height (m)
What happens when an object falls and there's no air resistance?
Energy lost from the g.p.e store = energy gained in the kinetic energy store
What does air resistance do when acting against falling objects?
It causes some energy to be transferred to other energy stores e.g. the thermal energy stores of the object and the surroundings
Elastic potential energy formula
E=1/2ke²
E.P.E(J) = 0.5 x spring constant(N/m) x extension²(m)
What is SHC? 
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
SHC formula 
E=mcθ
Change in thermal energy(J) = mass(kg) x SHC(J/kg/°C) x temperature change(°C)
What is the conservation of energy principle? 
Energy can be transferred usefully, or stored or dissipated (wasted energy), but can never be created or destroyed
What is power? 
The rate of energy transfer, or the rate of doing work
What is 1W equal to?
1J of energy transferred per second
Power Equation 1 
E=Pt
Energy transferred(J) = power(W) x time(s)
Power Equation 2 
W=Pt
Work done(J) = power(W) x time(s)
What is conduction? 
The process where vibrating particles transfer energy to neighbouring particles
Energy is transferred to thermal stores of the object - this energy is shared across the kinetic energy stores
What is thermal conductivity? 
A measure of how quickly energy is transferred through a material via conduction
What is convection? 
Where energetic particles move away from hotter to cooler regions
Energy is transferred to the thermal energy stores of the object and is shared across the kinetic stores
What do radiators create?
Convection currents
Convection currents - process
1) Energy is transferred from the radiator to the nearby air particles by conduction
2) The air by the radiator becomes warmer and less dense as the particles move quicker
3) The warm air rises and displaces the cooler air, which is then heated by the radiator
4) The previously heated air transfers energy to the surroundings - the air cools, becomes denser and sinks
What does lubrication do?
Reduce frictional forces
What does insulation do?
Reduce the rate of energy transfer by heating
Thermal insulation techniques 
1) Cavity walls - made up of an inner and outer wall with an air gap in the middle - the air gap reduces the amount of energy transferred by conduction through the walls
2) Cavity wall insulators - the air gap is filled with foam also reduces energy transfer by convection in the wall cavity
3) Loft insulation - reduces convection currents being created in lofts
4) Double-glazed windows - air gap between two sheets of glass that prevent energy transfer by conduction through the windows
5) Draught excluders - reduce energy transfers by convection around doors and windows
How do you improve efficiency?
1) Lubrication
2) Insulation
3) Making objects more streamlined
Efficiency - energy transfer equation
Useful output energy transfer divided by total input energy transfer
Efficiency - power equation 
Useful power output divided by total power input
Is any device 100% efficienct?
No
Where is wasted energy usually transferred? 
Thermal energy stores
How do thick walls prevent energy losses through heating?
They're made from a material with a low thermal conductivity - the thicker the walls, the lower the thermal conductivity, the slower the rate of energy transfer
What objects are usually 100% efficient?
Electric heaters - all the energy in the electrostatic energy stores is transferred to useful thermal energy stores
Fossil fuels (coal, oil, natural gas)
Non-renewable
Cause acid rain
Cause global warming
Reliable currently - they are finite, so they will run out eventually
Coal mining ruins the landscape
Oil spillages cause serious environmental problems
Energy resources used for transport
Petrol and diesel from oil - non-renewable
Coal (steam trains) - non-renewable
Bio-fuels - renewable
Energy resources used for heating
Natural gas - non-renewable
Coal - non-renewable
Electric heaters - non-renewable
Geothermal - renewable
Solar water heaters - renewable
Bio-fuels - renewable
Wind Power 
Renewable
Doesn't cause global warming
Doesn't cause acid rain
No pollution
No permanent damage to the landscape
Free - initial costs are high
Very noisy
Spoil the view
Not always reliable
Solar Power 
Renewable
Doesn't cause acid rain
Doesn't cause global warming
No pollution
Free - solar panels are expensive though
Not always reliable
Geothermal Power 
Renewable
Doesn't cause acid rain
Doesn't cause global warming
Free
Very little damage to the environment
Not very reliable - can only happen in certain places and there aren't very many of them
Hydroelectric Power 
Renewable
Reliable
Doesn't cause acid rain
Doesn't cause global warming
No pollution
Provides an immediate response to high demand
Free - initial cost is high
Big impact on environment and possible loss of habitat
Wave Power 
Renewable
Doesn't cause acid rain
Doesn't cause global warming
Free - initial costs are high
Not always reliable - waves die out when the wind drops
Disturbs the seabed and habitats of marine wildlife
Spoils the view
Hazard to boats
Tidal Power 
Renewable
Reliable
Doesn't cause acid rain
Doesn't cause global warming
No pollution
Free - initial costs are moderately high
Spoils the view
Alters the habitats of wildlife
Bio-fuels 
Renewable
Reliable
Doesn't cause acid rain
Carbon neutral
Free
Can cause global warming
Loss of natural habitat from destruction of forests
Cannot respond to immediate energy demands