Which one of the following heat transfers is an example of convection?

The correct answer is  Boiling water in a pot on a gas stove.

Key PointsExplanation of Heat Transfer by Convection

• Convection is the transfer of heat through the movement of fluids (liquids or gases).
• In the process of convection, heat energy is transferred by the mass motion of molecules within the fluid.
• As the fluid is heated, it becomes less dense and rises, while the cooler fluid sinks, creating a convection current.
• When boiling water in a pot on a gas stove, the water at the bottom of the pot is heated first.
• This heated water becomes less dense and rises to the top, while the cooler water descends to the bottom to be heated again, forming a continuous convection cycle.
• This movement of water molecules from hotter to cooler regions and vice versa exemplifies the process of convection. Hence, this statement is correct.

Analysis of Other Options

• Heating of food in a microwave oven:
  • Microwave ovens heat food using microwave radiation, which excites water molecules in the food, causing them to vibrate and generate heat.
  • This is an example of radiation, not convection. Hence, this statement is incorrect.
• Feeling the warmth in sun:
  • The warmth from the sun reaches us through radiation, as the heat travels through the vacuum of space in the form of electromagnetic waves.
  • This is not an example of convection, as there is no fluid medium involved in the transfer. Hence, this statement is incorrect.
• Heating a brass rod at one end and observing the temperature rise at the other end:
  • In this scenario, heat is transferred through the rod via conduction, where heat energy is passed from one molecule to the next through direct contact.
  • Conduction is different from convection, which involves fluid motion. Hence, this statement is incorrect.

Additional Information

• Heat Transfer Mechanisms:
  • Conduction: This is the transfer of heat through a solid material from one molecule to the next. It requires direct contact and is common in metals.
  • Convection: This involves the transfer of heat through the movement of fluids (liquids or gases). It is characterized by the formation of convection currents.
  • Radiation: This is the transfer of heat through electromagnetic waves without the need for a physical medium. The sun's heat reaching Earth is a prime example.
• Convection Currents:
  • Convection currents are created when a fluid is heated, becomes less dense, and rises. Cooler, denser fluid then moves in to take its place, setting up a cycle.
  • These currents are essential in various natural and man-made processes, such as ocean currents, atmospheric circulation, and heating systems.
• Applications of Convection:
  • Weather Systems: Convection currents in the atmosphere drive weather patterns and phenomena such as thunderstorms and sea breezes.
  • Geothermal Energy: Convection within the Earth's mantle plays a crucial role in the movement of tectonic plates.
  • Engineering: Convection is utilized in heating and cooling systems, including radiators and air conditioning units.