Physics Chapter 1

Chapter 1

Infrared radiation is energy transferred by electromagnetic waves. The higher the temperature of an object is, the more radiation it emits each second.

A dark, matt surface is a better absorber and a better emitter of infrared radiation than a light, shiny surface. A light, shiny surface is a better reflector of infrared radiation than a dark, matt surface.

A solid has a fixed volume and shape.A liquid has a fixed volume but no shape.A gas and a liquid can flow.A gas does not have a fixed volume.

A material called fibreglass is used to insulate a house loft. The handle of a frying pan is made of wood or plastic. A radiator in a central heating system is made from steel.

When a fluid is heated, t rises and mixes with the rest of the fluid. The fluid circulates and cools then it falls.

A liquid evaporates when its molecules escape into the surrounding air. When water cools on glass, water molecules in the air form a liquid on the glass. When a liquid condenses, it loses its faster-moving molecules and it cools.

Energy transfer through the walls of the radiator is due to conduction. Hot air in contact with the radiator causes energy transfer to the room by convection. Energy transfer to the room takes place directly due to radiation.

The small bucket of water will warm up faster, because it has a smaller mass and therefore the rate of temperature increase will increase.

Cavity wall insulation reduces the rate of energy transfer due to conduction. Aluminium foil behind a radiator reduces the rate of energy transfer due to radiation. Closing the curtains in winter reduces the rate of energy transfer due to conduction and 

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