Question

Is it convection, conduction, or radiation?

Answer 1

a) Warm air rises and cool air sinks : Convection

b) Sun rays warming a puddle : Radiation

c) An egg on a hot skillet : Conduction

d) Boiling water in a pan : Convection

e) Lava lamp : Conduction, Convection, Radiation

f) Feeling the suns heat on your neck : Radiation

g) Stepping on hot sand : Conduction

Explanation:

Convection: The mode of heat transfer involving fluids: liquids and gases due to convection currents produced in the fluids are termed as heat transfer due to convection. The dense cool air sinks, air currents push the warm air upwards and thus rising warm air is an example of convection. Boiling water is similarly warm water rising and cool water sinking; the provided heat produces convection currents. Boiling water in a pan is an example of convection.

Conduction: Heat transfer by direct contact between substances is called conduction. An egg on a hot skillet is fried by conduction. The hot frying pan transfers the heat to the egg. The metal frying pan and egg are in contact with each other. Stepping on hot sand makes us feel warm since the hot sand and our feet are in contact. Heat gets transferred through conduction.

Radiation: A puddle getting warm due to sun rays and feeling the sun's heat on our neck is clearly heat transfer due to radiation. Sun rays are electromagnetic waves that are capable of transferring heat energy. The materials are in no direct contact with each other in case of radiation.

A lava lamp shows all three heat transfer modes in different ways. The incandescent light bulb emits light and warms the metal at the bottom of the glass tube through radiation. The heat transfer between the metal below the tube and the liquid inside is through conduction. The flow of liquids with different densities (upward and downward) inside the glass tube is due to convection currents generated in the liquid mixture.