In cold weather, a bird fluffs up its feathers to help it stay warm.
How does fluffing up its feathers help the bird to reduce heat loss?
Air circulating between the feathers helps to heat up the bird's skin by convection.
Air trapped between the feathers reduces heat loss from the bird's body by convection.
The feathers conduct heat from the cold surrounding air to the bird's skin.
The feathers create a vacuum barrier that completely stops heat loss by radiation.
301 exam-style questions on CIE IGCSE Physics 2.3 Transfer of thermal energy, covering 2.3.1a Thermal conductors and thermal insulators, 2.3.1b Explaining thermal conduction, 2.3.2 Convection, 2.3.3a Thermal radiation, 2.3.3b Surface colour and texture, 2.3.3c Rate of emission and absorption of radiation, and 2.3.4 Consequences of thermal energy transfer. Each one has a worked solution and a mark scheme showing where the marks go.