topic 1 - energy Flashcards
What is a system?
an object or group of objects
what happens when a system changes?
the way the energy is stored changes when a system changes
what are the 8 energy stores? Give examples for each
magnetic - fridge magnets
internal (thermal) - human bodies, hot coffees
chemical - food, muscles, electrical batteries
kinetic - moving objects
electrostatic - thunderclouds
elastic potential - inflated balloons, stretched hairbands
gravitational potential - the energy of an object at height
nuclear - the energy stored in the nucleus of an atom
How does heating change the energy stored within a system?
- increases the energy of the particles
- this either raises the system’s temperature or, produces a change of state (e.g. solid to liquid)
How is work done to change the energy stored within a system?
- work is done when energy is transferred from one store to another
- when a force causes an object to move, work is done against frictional forces, causing the object’s temperature to increase and energy is lost as heat and sound to the surroundings
What is the relationship between work done when a current flows in a circuit?
- a current flows when there is a potential difference applied to the circuit
- this gives each charge an amount of energy
- this is the work done by the power supply when a current flows
what is specific heat capacity?
the amount of energy required to raise the temperature of a 1kg substance by 1°C
what is power?
the rate at which energy is transferred or the rate at which work is done
What is the law of energy conservation?
energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed
state any changes in the total energy of a ball that is kicked, assuming that no external forces act.
the total energy of the system remains constant due to the conservation of energy
what is waste energy?
the energy that is not used by the device for its desired purpose
What energy changes occur in a filament light-bulb?
- electrical energy is transferred into light and heat energy
- light is a useful energy form, heat is a waste energy
how can the efficiency of a system be increased?
- reducing waste output (by lubrication, thermal insulation etc
- recycling waste output (eg. recycling thermal waste energy as input energy)
Why can lubricating a bike’s gears allow the bike to go faster?
- adding a lubricant reduces friction
- so less work is done against friction
- so less energy is wasted as less is transferred to the surroundings as heat
- and the useful kinetic energy stored can remain higher
What is the consequence for energy transfer of a material with a high thermal conductivity?
the rate of energy transfer through the material is higher than for a material with a lower thermal conductivity
What is conduction?
the process where vibrating particles transfer energy to neighbouring particles
What is the singe device used to measure energy?
Joulemeter
What is the device used to measure current?
ammeter
what is the device used to measure the potential difference?
voltmeter
What is convection?
convection is where energetic particles move away from hotter to cooler regions
What happens to the density of air as it gets warmer?
the density decreased (so hot air will rise)
Why should the material used for house insulation have a low thermal conductivity?
- the higher the thermal conductivity the higher the rate of energy transfer by the material
- so a low thermal conductivity would transfer energy with a low rate and keep the energy in the house for longer
What are three methods of reducing heat loss in a building?
- double glazing
- loft and wall insulation
- thicker walls
How can the efficiency of a mechanical machine with moving parts be improved?
lubricate any moving parts to reduce the friction and therefore energy loss due to heating
