P2 Revision Flashcards
Black body radiation
The radiation emitted by a perfect black body
Perfect Black body
A body absorbing all the radiation that hits it
Infrared radiation
Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum
Specific heat capacity
Energy needed to raise the temperature of 1kg of a substance by 1C
Thermal conductivity
Property of a material that determines the energy transfer through it by conduction
How is energy transferred?
Mechanically(when a force does work)
Electrically(work done by moving charges)
By heating
By radiation
Main energy stored
Thermal energy store
Kinetic energy store
Gravitational potential energy
Elastic potential energy
Chemical energy
Magnetic energy
Electrostatic energy
Nuclear energ
What happens when a system changes?
Energy is transferred to/away from the system between different objects in the system or different types of energy stores
Closed systems
When the net change in the total energy of a closed system is alwahs zerk
An example of energy being transferred by heating
Energy’s transferred to the water from the kettle’s heating element to the water’s thermal energy store, causing the temperature of the water to rise
Work done=
Energy transferred
How is energy transferred in a kettle?
Energy’s transferred electrically to the thermal energy store of the kettle’s heating element, which transfers energy by heating to the water’s thermal energy store
How does friction between a car’s brakes and wheels do work?
This friction causes an energy transfer from the wheels’ kinetic energy to the thermal energy store of the surroundings.
How is energy transferred/work done in a collision between a car and stationary object?
The normal contact force between the car and object means energy’s transferred from the car’s kinetic energy store to otner energy stores e,g, the elastic potential and thermal energy stores of the object and car body. Some energy is also transferred away by sound waves.
How is energy transferred/work done when a person throws a ball upwards?
The initial force exerted by the person causes an energy transfer from the chemical energy store of the person’s arm to the kinetic energy store of the ball and the arm.
How can work be done?
When a current flows(work is done against resistance in a circuit), or by a force moving an object.
Kinetic energy store
Anything moving has energy in its kinetic energy store
Kinetic energy=
1/2 x mass x speed2
Gravitational potential energ store
Energy is transferred to this store due to the height it gains above ground
Gravitational potential energy=
Mass x gravitational field strength x height
For a falling object, with no air resistance, energy lost from the gravitational potential energy store=
Energy gained in the kinetic energy store
Impact of air resistance
Air resistance acts on all falling objects, causing some energy to be transferred to other energy stores, like the thermal energy stores of the object and surroundings
Elastic potential energy store
Stretching/squashing an object transfers energy to its elastic potential energy store
Elastic potential energy=
1/2 x spring constant x extension2