In this topic of IBDP Physics, we will learn about heat transfer.
Heat is thermal energy. It can be transferred from one place to another by conduction, convection and radiation. Conduction and convection involve particles, but radiation involves electromagnetic waves.
Conduction
Thermogram of a pan being heated on a stove.
In IBDP Physics, Heat energy can move through a substance by conduction.Metals are good conductors of heat, but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is conducted from the hot end of an object to the cold end.
The electrons in piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now charged metal ions. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These move through the structure of the metal, colliding with ions as they go.
Convection
In IBDP Physics, Liquids and gases are fluids. The particles in these fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection.
Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.
The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way,convection currentsthat transfer heat from place to place are set up.
Radiation
In IBDP Physics, All objects give out and take inthermal radiation, which is also calledinfrared radiation. The hotter an object is, the more infrared radiation it emits.
Light from the sun reaching earth
InIBDP Physics,Infrared radiation is a type of electromagnetic radiation that involves waves. No particles are involved, unlike in the processes of conduction and convection, so radiation can even work through the vacuum of space. This is why we can still feel the heat of the Sun, although it is 150 million km away from the Earth.
Some surfaces are better than others at reflecting and absorbing infrared radiation.
In IBDP Physics, If two objects made from the same material have identical volumes, a thin, flat object will radiate heat energy faster than a fat object. This is one reason why domestic radiators are thin and flat. Radiators are often painted with white gloss paint. They would be better at radiating heat if they were painted with black matt paint, but in fact, despite their name, radiators transfer most of their heat to a room by convection.
This is the end of this topic.
