Energy

Created by

Lorelie

Cards (72)

What happens when energy is transferred to an object 
The energy is stored in one of the object's energy stores.
How is energy transferred mechanically
by a force doing work
How is it transferred electrically 
Work done by moving charges
What are the other ways energy can be transferred
By heating or radiation
What happens when a system changes
Energy is transferred
What is a closed system
A system where neither matter nor energy can enter or leave
What's the net change in energy in a closed system
Always zero
Anything that's moving has energy in its
Kinetic energy store
A raised object has energy in its
Gpe store
What's the energy change for a falling object
Energy from gpe store is transferred into its kinetic energy store
Stretching or squashing an object can transfer energy to which energy store?
Elastic potential energy store
What is specific heat capacity
The amount of energy needed to change the temperature of 1kg of a substance by 1 degree.
What is the conservation of energy principle
Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
What's it called when not all energy is transferred usefully
Dissipated energy
What is power 
The rate of energy transfer or work done
What s power measured in
Watts
What does a powerful machine do 
Transferred a lot of energy in a short space of time
What is conduction 
The process where vibrating particles transfer energy to neighbouring particles
What does conduction mainly occur in
Solids
What happens to the particles in a part of an object being heated
They vibrate more and collide with each other
What do these collisions cause
Energy transfer
What is thermal conductivity 
A measure of how quickly energy is transferred through a material via conduction
Convection occurs only in
Liquids and gasses
What is convection 
Energetic particles move away from hotter to cooler regions
What happens when you heat a region of a gas/liquid
The particles move faster and the space between particles increases
What does this cause
It causes the density to decrease
The warmer and less dense region will...
Rise above the denser cooler region
If there is a constant heat source...
A convection current can be created
What does lubrication reduce
Frictional forces
What does insulation reduce 
The rate of energy transfer by heating
How can you prevent energy losses by by heating
Have thick walls with a lower thermal conductivity
What does this do
Slows the rate of energy transfer (the building will cool more slowly)
What are examples of thermal insulation 
Cavity walls, loft insulation, double glazed windows and draught excluders
What is a cavity wall 
made up of an inner and outer wall separated by a cavity filled with air
What does the air gap do
Prevents energy loss by conduction
What happens if you fill the air gap with foam
Reduces energy transfer by convection
What does loft insulation do
It reduces energy transfer by convection, by preventing convection currents from forming.
How does double glazing reduce energy transfer
Prevents conduction through windows
How does a draught excluder help reduce heat loss?
Reduces energy transfers by convection
What is a more efficient energy transfer
An energy transfer with less dissipated energy