Energy stores and transfers Flashcards
What is a closed system?
where there is no change to the total energy in the system
energy can flow in or out of the system, but there is no transfer of mass
(e.g. a pan of water being heated with a lid on it)
Name four ways in which energy can be transferred
mechanically - by a force moving through a distance
electrically - by the use of electric current
thermally - because of a difference in temperature
radiation - by waves such as electromagnetic or sound
(some of the energy will be usefully transferred, and some will be wasted/dissipated)
Name and give the definitions of the eight main types of energy
Gravitational potential energy - the energy that objects store when they move up
Light energy - energy carried by light waves
Elastic potential energy - energy stored when materials are stretched/squashed/bent
Sound energy - energy carried by sound waves/ what noisy objects give out
Electrical energy - the energy that electrical currents transfer
Thermal energy - the energy that hot objects have
Kinetic energy - energy that moving objects have
Chemical potential energy - energy released by chemical reactions
Name the eight main types of energy/energy stores and give an example
chemical (fuel, food, battery)
kinetic (moving objects)
gravitational potential (raised mass)
elastic potential (stretched spring)
thermal (hot objects)
magnetic (two magnets) OR/sometimes exchanged for light energy (light waves)
(magnetic energy is different to light energy)
electrical/electrostatic (two charges)
nuclear (radioactive decay) OR/sometimes exchanged for sound energy (sound waves)
(nuclear energy is different to sound energy)
How can energy transfers from one store to another be represented?
energy flow diagrams
Give one example of an energy flow diagram
torch:
chemical (battery) -> light (useful)
-> thermal energy (wasted)
blender:
electrical energy -> wasted thermal energy
-> wasted sound energy
-> kinetic energy
photosynthesis:
light energy -> chemical potential energy
In an energy flow diagram, how is the wasted energy shown?
in an arrow pointing above the other products
What type of energy is almost always wasted?
thermal
What is the rule related to energy?
energy is never created or destroyed, but it can be transferred
(conservation of energy)
What is the template for an energy flow diagram?
Input -> [] -> wasted outputs
-> useful outputs
Draw a flow diagram to show the useful and wasted energy transfers for a camping gas stove.
chemical (camping gas + oxygen) -> thermal (pan and air) wasted
- > thermal (hot water in pan)
- > wasted light energy
both the thermal energies are transferred thermally
the light energy is transferred via radiation
Draw an energy store flow diagram for a car driving up a hill
chemical store (decreases) -> (mechanical) (energy transfer) -> kinetic store (increases) + gravitational potential store (increases) + thermal store (increases)
When a person lifts a 2kg mass above the ground, the energy stores change.
Draw a possible flow diagram for the transfer and explain how the energy stores change
chemical store -> kinetic store + gravitational potential store -> gravitational store + thermal store
The initial energy store is chemical energy from food. The energy transfer is mechanical.
The chemical store is transferred to an increasing kinetic store due to its motion and an increasing gravitational potential energy store due to the increase in height.
Finally, all of the chemical store has been transferred to gravitational store with some being wasted as a thermal store and dissipated to the surroundings.
