Q111
General SciencePhysics
The freezing chest in refrigerator is kept near the top because
- a.it is convenient to use.
- b.it reduces cost.
- c.it cools the remaining space by the process of conduction.
- d.convection currents are set up.
Answer: (D) convection currents are set up.
Air cooled by the freezing compartment becomes denser and sinks, while warmer, lighter air from below rises to take its place and gets cooled in turn. These convection currents carry cold air through the whole cabinet, which is possible only if the cooling unit is at the top. Conduction is negligible because air is a very poor conductor of heat, and convenience or cost is not the reason. For the same reason air-conditioners are fixed high on a wall, while room heaters are kept near the floor.