Energy Resources and Transfers Flashcards
State the 8 main stores of energy
-Chemical
-Gravitational
-Thermal
-Electrostatic
-Kinetic
-Elastic
-Magnetic
-Nuclear
Define conservation of energy
Energy cannot be created or destroyed, only change from one form to another.
What are the four main transfer types between energy stores?
-Mechanically (by force)
-Electrically (current flow)
-Heating (conduction, convection, radiation)
-Radiation (light and sound)
How can energy be changed through work done by forces?
A force converts energy mechanically by work done. Eg. If moving object is travelling upwards, its kinetic energy is converted to GPE by work done against its weight
A skateboarder starts at rest at the top of a hill, she pushes herself down a rough hill and comes to rest at the bottom. What energy changes take place?
-Start= GPE + Work by pushing herself
-Riding down =GPE→KE and friction
-All energy lost through heting the surroundings through the friction between the ground there is no KE and she’s at rest.
How can energy be transferred through electrical equipment?
Energy is stored as chemical in the battery. Then current converts chemical energy into other forms electrically.
State the equation used to calculate “efficiency”
Efficiency= useful energy/total energy x100
What changes are involved when a ball (initially stationary), rolls down a hill?
-GPE turns into KE as it rolls downwards
-The speed will increase
Define wasted energy
The energy that is not used up by the device for its desired purpose is the waste energy.
In which ways can thermal energy be transferred?
-Conduction
-Convection
-Radiation
Define conduction
When heat is transmitted in solids through collisions between neighboring atoms or molecules.
Define convection
Heat is transferred in gases and liquids by movement from hotter to cooler regions.
Define radiation
Energy that comes from a source and travels through space at the speed of light.
Explain how surfaces can be adjusted for heat transfer by radiation
-Black dull surfaces are good emitters/absorbers but bad reflectors of thermal radiation. White and shiny vice versa.
Define thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat.
How does the thickness of a building’s walls affect the rate of cooling?
The thicker the building walls are the further heat has to travel to escape, hence as you increase the thickness you decrease the rate of cooling
How can you reduce unwanted energy transfer.
-Insulation in walls and ceilings.
-Double glazed windows
-Curtains
Equation for the work done on an object
W = F x d
Work=Joules
Force=N
d=Metres
Relationship between work done on an object and energy transfer?
W=∆E
State the equation used to calculate the change in gravitational potential energy.
∆GPE = mxgx∆h
GPE=Joules
Change in vertical height=m
Equation used to calculate kinetic energy.
KE= 1/2mv²
KE=Joule
mass=kg
speed=m/s²
What is meant by power in physics
-Rate at which energy is transferred.
-Work done per unit of time
State the equation used to calculate the power of a device
Power(Watts)=Work done(J)/Time (s)
W/PxT
What is another way of describing a watt?
1 joule per second
