Heat And Engergy Part 1 Flashcards
What do all objects emit? What happens when the object is hotter?
Infra radiation. When the object is hotter the more infra red it emits.
What are light and shiny surfaces best at?
At reflecting thermal radiation
What are dark and matt surfaces best at?
At emitting and adsorbing thermal radiation
What is the best conductor of heat and why? What energy does it transfer?
Metal because they have free electrons which diffuse (spread out) and collide with other free electrons and ions. In this way it transfers kinetic energy.
What materials are good insulators and why?
Wool and fibreglass because they contain air trapped between the fibres.
What materials are poor conductors and why?
Wool and fibreglass because they have no free electrons.
What is convection? What is it caused by? How is it created?
Convection is the circulation of a fluid. It is caused by heat. It is created when hot,less dense fluid rises and cold, denser fluid sinks.
Explain how a flask works…
It keeps liquids warm because of the way its designed. The vacuum between the walls reduces heat transfer by conduction and convection. The silvered inner surface reduce heat transfer by radiation.
What are all the names of the energy changes? (9)
Chemical energy, kinetic energy, gravitational potential energy, elastic potential energy, electrical energy, light energy, sound energy, heat energy, nuclear energy
Can energy be created or destroyed ? Give an example
No. When an object falls, its gravitational potential energy decreases and its kinetic energy increases. This is the conservation of energy.
What is useful and wasted energy?
Useful energy is in the form we need it. Wasted energy is not useful.
What is the sankey diagram used for?
It is used to represent the energy transfers in a devise
What happens to both useful and wasted energy when it is transferred to its surroundings ?
It becomes warmer
What is energy measured in?
Joules
How is efficiency calculated?
Efficiency(%) = (useful energy transferred/ total energy supplied) x 100
Or
Efficiency(%) = ( useful power output/ total power input) x 100
What is the maximum machine efficiency?
100%
How can efficiency be improved?
By reducing friction, reducing electrical resistance etc.
What is 1kW
1000W
Explain the process of conduction through metals
In the metal there are free electrons. It gains kinetic energy. It transfers energy into ions and it helps tranfers energy.
Why is a matt black pot better than a shiny one?
Because it absorbs heat NOT LIGHT
What is thermal (infra-red) radiation and what can it travel through?
Electromagnetic radiation and it can travel though a vacuum.
What is conduction?
It is when heat energy can move through a substance
What is an insulator?
They are poor conductors of heat?
What is thermal radiation?
It is what all objects give out and take in
What is Infrared radiation?
It is the same as thermal radiation which is what all objects give out and take in
What does emit mean?
It means to give off.
What is electromagnetic radiation?
Its the light things u learnt last year
What does radiation mean?
It is an energy that comes from a source and travels through some material or space.
What does heat transfer mean?
It is the movement of thermal energy from one thing to another thing of different temperatures.
