Topic 1 Energy GCSE physics Flashcards
What are the energy stores?
thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear (energy stores)
What are the ways energy is transferred?
mechanically (by force doing work), electrically (work done by moving charges), heating/radiation
What happens when a system changes?
- energy is transferred
- it can be transferred into or away from the system
- between different objects in the system or between different types of energy stores
What are closed systems?
- systems where neither matter nor energy can enter or leave
- net change in total energy is always zero
When can work be done?
- when current flows
How does energy transfer when a person throws a ball?
- initial force exerted by a person to throw a ball upwards does work
- causes an energy transfer from the chemical energy store of the persons arm to the kinetic energy store of the ball and arm
How does energy transfer when a ball is dropped from a height?
- accelerated by gravity
- gravitational force does work
- energy transferred from balls gravitational potential energy store to its kinetic energy store
How does energy transfer between a cars breaks and its wheels?
- friction between break and wheels does work as it slows down
- energy transfer from wheels kinetic to thermal energy stores of the surroundings
How is energy transferred during a collision between the car and a stationary object?
- normal contact force between car and the object does work
- causes energy to be transferred from the cars kinetic energy to other energy stores
(elastic potential and thermal of object and car body)
What is the conservation of energy principle?
- energy can be transferred usefully, stored or dissipated but can never be created or destroyed
Is all of the energy transferred between stores useful?
- not all energy is transferred usefully
- some energy is dissipated
How is energy wasted with a mobile phone?
- energy usefully transferred from chemical store (battery)
- some is dissipated to thermal energy of the phone (phone feels warm when you use it for a while)
How is energy transferred in a closed system? (cold spoon)
- cold spoon dropped from an insulated flask of hot soup which is then sealed
- energy transferred from thermal store of soup to useless thermal energy store of spoon
- energy transfers have occurred within the system but no energy has left the system (net change =0)
What is power?
- rate of energy transfer or the rate of doing work
How can you calculate power?
power= energy transferred/time
What is a “powerful machine”?
- one which transfers a lot of energy is a short space of time
Where does conduction mainly occur?
- in a solid
What is conduction?
- conduction is the process where vibrating particles transfer energy to neighbouring particles
What is thermal conductivity?
- measure of how quickly energy is transferred through a material in this way
Where is energy transferred to an object by heating transferred to?
- thermal stores of object
What happens to the particles during conduction?
- particles in the part of the object being heated vibrate more and collide with each other
- collisions cause energy to be transferred between particles kinetic energy store
Does the process of conduction continue throughout the whole object?
- yes
- until energy is transferred to the other side of the object
- then transferred to thermal energy stores of the surroundings
What is convection?
- where energetic particles move away from hotter to cooler regions
Where does convection occur?
- only in liquids and gases
How is convection different to conduction in terms of moving particles?
- unlike solids, the particles in a liquid are able to move
- when you heat, the particles move faster and the space between individual particles increases
What do radiators create?
- convectional currents
- heating a room with a radiator relies on creating convection currents in the air of the room
How is energy transferred in radiators?
- from radiator to nearby air particles by conduction
- air by radiator becomes warmer and less dense
- warm air rises and is replaced by cooler air
- cooler air is then heated by the radiator
What is a convection current (with the radiator)?
- previously heated air transfers energy to the surroundings
- it cools, becomes denser and sinks
- cycle then repeats causing a flow of air to circulate around the room (convection current)
What can lubricants be used for?
- reduce the friction between the objects surfaces when they move