Energy Flashcards
What are the three main methods of heat transfer?
Conduction - Mainly in solids, liquids are poor conductors, almost none in gases
Convection - Only in liquids and gases
Radiation - In a vacuum
What are poor conductors called?
Insulators
How does convection in air occur?
When the fastest moving particles in a hot region of a gas or liquid move to cool region, taking their heat energy with them.
Why does convection only occur in liquids and gases?
In solids, the atoms are not free to move from place to place, so cannot carry their heat energy with them
What is radiation?
The method of heat transfer that takes place without the need for any particles.
This is how Earth receives heat energy from the sun
What is power?
The amount of energy transferred in one second, or the amount of work done in a second
Power = Work done / Time taken
P = W / T
What is work done?
When a force causes movement
Work done = Force x Distance
W = F x d
What is efficiency?
A way of describing how good a device is at transferring energy from one form into another in and intended way.
Efficiency = Useful energy output / Total energy input
Efficiency has no units because it is a ratio, but it can be recorded as a decimal or as a percentage
What is the principle of the conservation of energy?
Energy cannot be created nor destroyed, it can only be transferred from one form into another
What is kinetic energy?
The kinetic energy of an object is the energy it has because it is moving
Kinetic energy = 1/2 mass x velocity^2
KE = 1/2 mv^2
