Energy Flashcards
Name 4 energy stores
- Kinetic
- Gravitational potential
- Magnetic
- Electrostatic
3 ways energy can be transferred in a system?
- In or out the system
- To and from different objects
- To and from different stores
What is a closed system
Matter nor energy can leave or enter
What is always the net change in the total energy of a closed system?
0
2 ways energy can be transferred and how?
- Heating - energy is transferred into the water’s thermal energy store from the kettle’s heating element
- Doing work - transfers energy by providing a force
Equation for kinetic energy store?
E = 1/2mass x velocity^2
How does kinetic energy transfer?
When an object speeds up, energy is transferred to this store, when an object slows down, energy is transferred away
Equation for GPE
E = mass x gravitational field strength x height
How do falling objects transfer energy?
Energy from the object’s GPE store is transferred into the object’s kinetic store
Why does energy lost from GPE = energy gained in kinetic not always work for falling objects?
Air resistance causes some energy to be transferred to other energy stores
Equation for elastic potential energy?
E = 1/2spring constant x extension^2
Equation for specific heat capacity?
Change in energy = mass x specific heat capacity x temperature change
What is specific heat capacity?
The amount of energy needed to heat 1kg of an object up by 1 degree Celsius
What is the conservation of energy principle?
Energy can be transferred, stored or dissipated, but never created or destroyed
How can energy be dissipated?
In a phone, energy from the battery’s chemical store is usefully transferred, whilst some is transferred to the thermal energy store
What is wasted energy?
Energy being stored in a way that is not useful
Describe energy transfer in a closed system of a spoon in soup.
Assuming a lid is a perfect insulator, energy is dissipated from the thermal energy store of the soup to the useless thermal store of the spoon, cooling the soup down, although no energy has left the system
Equation for power?
P = energy transferred (or work done) / time
What does power mean?
Rate of energy transfer
How does conduction work?
- Energy is transferred to an object’s thermal energy store by heating
- Particles in this part of the object begin vibrating and collide with adjacent particles, transferring to kinetic energy stores
What is thermal conductivity?
How quickly energy is transferred through an object
How does convection work?
- Energy is transferred to a liquid/ gases thermal energy store by heating
- The faster moving particles then move further apart, reducing density
- The less dense substance, then moves above the denser, cooler substance
How do radiators heat rooms?
- Energy is transferred from the radiator to nearby air particles by conduction
- Air particles by the radiator move quicker and spread out, reducing density and moving above the denser air
- Colder takes the place of the hot air and a convection current is created
How do lubricants reduce unwanted energy transfer?
Lubricants reduce friction, which can cause some energy to be dissipated to an object’s thermal store
4 ways energy loss can be prevented in houses?
- Cavity walls - have an air gap to reduce energy loss through conduction out of the house
- Loft insulation - reduce convection currents in a loft
- Double glazed windows - air gap between two windows reduces conduction
- Draught excluders - reduce convection around doors and windows
Efficiency equation?
Efficiency = useful energy output/ total energy input
What does efficiency mean?
How much energy is transferred usefully
Example of a 100% efficient device?
Electric heater
Non renewable energy sources used in transport?
- Petrol/ diesel
- Coal
Renewable energy sources used in transport?
Biofuel
Non renewable energy sources used for heating
- Natural gas
- Coal
- Electric heaters
Renewable energy sources used for heating?
- Geothermal
- Solar water heaters
- Bio fuel
4 Disadvantages of wind power?
- Spoil the view
- Noise pollution
- Unreliable - must be windy
- Impossible to increase supply in high demand
3 Disadvantages of solar cells?
- Expensive to manufacture
- Can’t increase supply in high demand
- Only work in the daytime
2 Disadvantages of geothermal?
- Not many suitable locations
- Expensive to build a plant
3 Disadvantages of hydroelectric?
- Flooding valleys destroys habitats
- Can ruin landscapes
- Initial costs are high
3 Disadvantages of waves?
- Disturbed sea bed and habitat destruction
- Hazard to boats
- Unreliable - waves rely on wind
Disadvantages of tidal barrages?
- Preventing access to boats
- Ruins habitats
- Spoils view
Disadvantages of bio fuels?
- Only carbon neutral if plants are grown at the same rate as burning
- Cannot respond to immediate energy demands
- Plants for bio fuels means less space for people to grow foods
Advantages of non renewable energy?
- Reliable
- Can increase supply in times of high demand
- Running costs are low
4 Environmental disadvantages of non renwable energy?
- Greenhouse effect
- Sulphur dioxide causes acid rain which damages wildlife
- Oil spills kill marine life
- Nuclear waste is very dangerous
Why does the UK aim to be more renewable?
Pressure from other countries and the public
Why is renewable use limited?
- Scientists can’t make people change
- Renewable plants mean higher costs for the population through tax
- Ethical arguments of making people live next to wind farms
