Energy Transfers (8k) Flashcards
What is the equation for power?
Power = energy/time
What is the equation for efficiency?
Efficiency= useful energy transferred/ total energy applied x 100%
How do you work out payback time?
_____________________cost of change
payback time = ___________________
savings per year
Define evaporate
When a liquid turns into gas
Define joule (J)
A unit for measuring energy.
How many joules are in a kilojoule
There are 1000 joules in a kilojoule
Define kilowatt (kW)
A unit for measuring power. There are 1000 watts (W) in 1 kilowatt (kW).
How many watts are in a kilowatt?
There are 1000 watts (W) in 1 kilowatt (kW).
Define internal energy
The energy stored in the movement of particles. Sometimes called thermal energy.
Define conduction
The way energy is transferred through solids by heating
Explain conduction
Conduction takes place in solids and can also happen in liquids (although not very well).
The particles in a solid are held together tightly. When they gain energy they vibrate faster and further, and the vibrations are passed on. Metals are the best conductors. Most other solids are poor conductors.
Define convection
The way energy is transferred by heating in fluids/liquids
Define convection current
A flow of liquid or gas caused by part of it being heated or cooled more than the rest
Define Infrared radiation
A way of transferring energy by heating that does not need a medium (material). Infrared radiation can travel through transparent things and a vacuum (empty space).
Define thermal conductor
A material that allows internal (thermal) energy to be transferred through it easily.
Define thermal insulator
A material that does not allow internal (thermal) energy to be transferred through it easily
Define accurate
A measurement that is close to the true value.
Define precise
Measurements that are close to one another but not as close to the correct value
Define random error
An error that can be different for every reading
Define efficiency
A way of saying how much energy something wastes
Define power rating
The number of joules of energy an appliance uses every second
Define Sankey diagram
A diagram showing energy transfers, where the width of each arrow is proportional to the amount of energy it represents.
Define kilowatt-hour (kWh) and how many kilojoules is it equal to?
The amount of energy used by a 1 kilowatt (kW) appliance in one hour. It is equal to 3600 kilojoules (kJ).
Define payback time
The time it takes to get back (in energy savings) the money you spent on making an energy-saving change.
