Topic 3 (thermal Physics) Flashcards
Three main methods of heat transfer?
Conduction - in solids
Convection - in liquids and gases
Radiation - in all media, including a vacuum
What is conduction?
It is a method of heat transfer which occurs in solid materials
What happens when a solid is heated?
The atoms and free electrons gain kinetic energy, increasing collisions and transferring heat. Metals are better conductors of heat because they have lots of free electrons and are able to transfer energy more readily
What is convection?
It is a method of heat transfer which occurs in liquids and gases. When heat is applied the molecules adjacent to the heat source gain kinetic energy and expand, resulting in a decrease in density
Equilibrium meaning
A state of physical balance
What is radiation?
It is the only method of heat transfer which takes place in a vacuum
What are Matt black objects?
They are the bet absorbers and emitters if radiant heat and white shiny objects are the worst absorbers of radiant heat
What is background radiation?
It is caused by radioactive substances in rocks and soil and by cosmic rays and some come from waste products and man made sources
Three types of radiation?
Alpha (least penetrating)
Beta
Gamma(most penetrating)
Medical uses of radioactivity
Medical tracers
Radiotherapy
PET scans
Famous physicists who studied radioactivity?
Henri Becquerel - joint Nobel prize winner for discovery of radioactivity
Marie Curie - first female to win a Nobel prize
Ernest Rutherford - famous for his gold leaf experiment.
What can alpha, beta and gamma rays not go past?
Alpha - paper
Beta - aluminium
Gamma - it can go through lead
