Paper 2: Section 8- Energy – forces doing work Flashcards
What is a system?
A single object or a group of objects that you’re interested in- it can be defined how you want.
What happens when a system changes?
Energy is transferred
How is the energy transferred when a system changes?
It can be transferred into or away from the system, between different objects in the system or energy stores.
What happens to some energy whenever a system changes?
Some energy dissipates and is stored in less useful ways.
What is the efficiency of a transfer?
Useful energy transferred by device/ total energy suppliedto device
What is a closed system?
A system defined so that the net change in energy is zero.
What are three ways energy can be transferred?
. Through work done by forces
. By electrical equipment
. By heating
What do the boxes and the arrows in an energy transfer diagram?
Boxes- stores
Arrows- transfers
What is the definition of work done?
The amount of energy transferred.
How do you calculate work done?
E= F x D
How many joules of work is done when a force of an neutron causes and object to move 1 metre?
1 joule of work:
IJ = 1Nm
When a force does work often, what happens?
It causes a rise in temperature as energy is dissipated to the thermal energy stores.
What is ment by ‘power’?
The rate of energy transfer
What is the unit for power?
Watts (W)
How many watts are equal to 1J/s?
1W = 1J/s
