Convection - Oxford AQA IGCSE Physics

What causes convection currents?

• Changes in temperature leading to changes in density.

• The movement of tectonic plates.

• The rotation of the Earth.

• The presence of magnetic fields.

What is convection?

• A method of thermal energy transfer through solids.

• The main way that thermal energy is transferred through liquids and gases.

• A process of energy transfer that occurs only in solids.

• A type of radiation that occurs in a vacuum.

Describe the process of convection when a liquid or gas is heated.

• The molecules move slower and come closer together, making it denser.

• The hot liquid or gas rises while cooler liquid or gas moves in to take its place.

• The temperature remains constant as the liquid or gas is heated.

• The liquid or gas cools down and contracts, becoming denser.

In which states of matter does convection occur?

• Solids

• Liquids and Gases

• Only in Gases

• Only in Liquids

Why can't convection occur in solids?

• Convection requires the movement of particles, but in solids, particles are held in a fixed position.

• Convection is only possible in liquids and gases due to their fluid nature.

• Solids do not have any particles to move around.

• Convection occurs in solids but is very slow compared to liquids.

What happens to a liquid or gas when it cools?

• The molecules speed increases and they move further apart, making the fluid less dense.

• The molecules speed decreases and they move closer together, making the fluid more dense.

• The temperature of the liquid or gas remains constant, and its density does not change.

• The liquid or gas evaporates completely when cooled.