Energy Flashcards
What are the 7 different energy stores?
Chemical
Kinetic
Gravitational Potential
Elastic Potential
Thermal
Magnetic
Nuclear
How can energy be transferred?
Heating, waves, electric current or force
What is the name of the energy stored by a moving object?
Kinetic
What happens to dissipated energy?
It spreads out to the surroundings
What is the equation for kintetic energy?
1/2 x mass x velocity^2
What is the equation for gravitational potential energy?
mass x gravity x height
What is the equation for elastic potential energy?
1/2 x spring constant x extension^2
What is the principle of conservation of energy?
Energy cannot be created or destroyed.
What does the conservation of energy apply to?
all energy changes
What is meant by a closed system?
No energy transfers take place out of or into the energy stores of the system.
Complete the sentence: Energy transfers can take place between ___________ __________ within a ___________ _________.
energy stores, closed system
True or false : The total energy of a closed system is never the same before and after energy transfers.
False
What is work done?
Energy transferred when an object is moved by a force.
What is the equation linking force, work done and distance moved?
work done = force x distance moved
What is work done to overcome friction transferred as?
energy to the thermal energy stores of the objects that rub together and to the surroundings
What happens to the gravitational energy store of an object when its height increases?
Increases
What is the gravitational field strength on earth?
9.8N/kg
How many grams in 1kg?
1000g
What does the kinetic energy of an object depend on?
Its mass and speed
What is elastic potential energy?
The energy stored in an elastic object when work is done on it.
What is Hooke’s law?
Force = spring constant x extension
What is useful energy?
energy transferred to where it is wanted in the way it is wanted
What is wasted energy?
energy that is not usefully transferred
What is the most common energy store of wasted energy?
Thermal
What is the equation for efficiency?
efficiency = useful output energy/ total input energy x100
True or false: No energy transfer can be more than 100% efficient.
True
What are the 4 reasons why devices waste energy?
friction, resistance of a wire, air resistance, sound
How can friction be reduced?
Lubricate the moving parts
How can the resistance of a wire be reduced?
use wires with little electrical resistance
How can air resistance be reduced?
Use streamline shapes
How can sound be reduced?
cut out noise
What is the wasted energy of a light bulb?
thermal
What is the wasted energy of an electric heater?
sound and light
What is the wasted energy of an electric toasted?
thermal heating the air around it
What is the wasted energy of a hairdryer?
Sound and thermal
What is the equation for power?
power = energy transferred/ time
What is power?
The energy supplied to a motor per second
What is power measured in?
Watts
What are the best conductors of energy?
metals
What type of materials are the best insulators?
non-metal materials, e.g. wool and fibreglass
What is thermal conductivity?
the energy transfer by conduction through a material
What does the energy transfer per second through an insulator depend on?
the temperature difference, thickness of material, thermal conductivity of the material
What type of radiation does the sun emit?
infrared radiation
True or false: All objects emit and absorb infrared radiation.
True
Complete the sentence: The ________ an object is the more infrared radiation it emits in a ________ _______.
hotter, given time
What is blackbody radiation?
radiation emitted by a body that absorbs all the radiation incident on it, it doesn’t reflect any
What type of surface emits less radiation than a dark, matt surface?
light, shiny
What type of surface emits more radiation than a light, glossy surface?
dark, matt
What does the temperature of the earth depend on?
the rate that light and infrared radiation is reflected, absorbed and emitted by the earth
What is specific heat capacity?
The energy needed to raise the temperature of 1kg of a substance by 1°C.
When a substance is heated, what does the temperature rise depend on?
the amount of energy supplied, the mass of the substance, what the substance is
What is the equation for specific heat capacity?
energy transferred = mass x specific heat capacity x temperature change
What is specific heat capacity measured in?
J/kg°C
What is the required practical for specific heat capacity?
Method:
- Add 1kg of oil in a beaker
- Add immersion heater and thermometer
- Record starting temp
- Wrap in insulating foam
- Connect a joule-meter and power pack
- time for 30 mins
- Record the joules and final temp
- calculate specific heat capacity
What is the specific heat capacity of water?
4200J/kg°C
How are houses heated?
- electric or gas heaters
- oil or gas central heating systems
- solid fuel in stoves or fireplace
What can be done to reduce heat loss from a house?
- Loft insulation
- Aluminium foil between radiator and wall
- Double-glazed windows
- Cavity wall insulation
What do solar panels do?
absorb infrared radiation from the sun to generate electricity directly or to heat water directly
What is cavity wall insulation?
insulation material used to fill the cavity between two brick layers of an external house wall
Where does most energy come from?
Burning fossil fuels, mostly gas or oil or coal
How do power stations work?
The burning of fuel heats water which produces steam. The steam drives a turbine that turns an electricity generator.
What is a biofuel?
Fuel taken from living or recently living organisms.
Give one example of a biofuel?
animal waste
What can biofuels be used instead of?
fossil fuels
Why are biofuels renewable?
The biological source can regrow or is continually produced, so it is used at the same rate that it is replaced
Why is biofuel carbon neutral?
The carbon that the living organism takes in from the atmosphere as CO2 can balance the amount that is released when the biofuel is burnt.
What is nuclear power?
when nuclear fuel takes energy from atoms
What fuel is in a nuclear power station?
uranium
How is nuclear power generated?
The nucleus of the uranium atom is very unstable and can split in two. Energy is transferred from the nucleus when this happens.
The core becomes hot. The energy transferred by the coolant from the core is used to heat water to generate steam.
How does wind power generate electricity?
The force of the wind turns the turbine blades which then turns a generator.
How does wave power generate electricity?
Waves make a floating generator move up and down. The motion turns the generator do it generates electricity.
How does hydroelectric power generate electricity?
When rainwater that collected in a reservoir flows downhill, it drives turbines that turn electrons generators.
How does tidal power generate electricity?
It traps water from reaching each high tide behind a barrage. The high tide is then released through turbines that turn a generator to generate electricity.
What is used to connect wave power and tidal power to the national grid?
underwater cables
What types of renewable power are unreliable?
wind, wave and hydroelectric
How does solar power generate electricity?
They absorb the suns energy to generate electricity directly
OR
They have water pumping through them that gets heated by the suns energy causing a turbine to turn
How does geothermal energy generate electricity?
Cold water is pumped down into the hot rocks beneath the earths surface. The heat turns the water to steam which then travels up a pipe causing a turbine to turn.
Where does geothermal energy come from?
energy transferred by radioactive substances deep inside the earth
What is the issue with fossil fuels?
they release greenhouse gases which causes global warming and sulfur dioxide which causes acid rain, they are also non-renewable
What are the advantages of nuclear power?
No greenhouse gases produced and much more energy is transferred from each kg of uranium than fossil fuels
What are the disadvantages of nuclear power?
Used fuel rods contain radioactive waste which must be stored safely
An explosion could release radioactive material over a wide area
What are the advantages of renewable energy?
- Never run out
- do not produce greenhouse gases or acid rain
- do not create radioactive waste products
What are the disadvantages of renewable energy?
- Can’t meet the world demand
- Noise pollution
- Visual pollution
- Can disturb wildlife
- Habitats flooded by dams
- Require lots of
- can be unreliable
How is the variable demand for electricity met by?
- nuclear and coal fired power stations
- gas-fired power stations
- renewable energy resources when demand is high and low
What can be used to reduce the amount of carbon released by power stations?
carbon capture technology
