Answer :
Let's go through each part of the question step-by-step to understand the concepts involved in heat transfer:
Multiple Choice Question:
- A red hot metal ball is hanging from the roof with a metal chain. It is losing heat by:
- (a) conduction and radiation
- (b) conduction and convection
- (c) convection and radiation
- (d) conduction, convection and radiation
Explanation:
Conduction occurs when heat is transferred through a material, like the metal chain, by direct contact. The hot metal ball transfers heat to the chain through conduction.
Convection involves the transfer of heat by the movement of fluids (liquids or gases). Since the metal ball is hanging and surrounded by air, it loses heat through convection as the hot air around it rises and cooler air takes its place.
Radiation is the transfer of heat in the form of electromagnetic waves. The red hot metal ball emits infrared radiation to the surrounding environment.
Therefore, the most comprehensive answer is (d) conduction, convection and radiation since all these modes of heat transfer apply.
Fill in the Blanks:
Copper is a good conductor of heat.
- Copper is widely used in cooking and electronics because it transfers heat efficiently.
The heat of the Sun comes to us through the process of radiation.
- Radiation allows energy to travel through the vacuum of space as electromagnetic waves, reaching Earth as sunlight.
Temperature is the measure of hotness or coldness.
- It tells us how warm or cool an object or environment is using units like Celsius or Fahrenheit.
Liquids expand less than gases.
- When heated, gases expand more because the molecules move faster and spread out more than in liquids.
Heat transfers in solids through conduction.
- In solids, particles are closely packed, so heat easily flows from one particle to another.
Three modes of transfer of heat are conduction, convection, and radiation.
- These are the primary ways heat energy moves from one place to another.
The dark-coloured clothes absorb heat and make us feel warm and comfortable in winters.
- Dark colors absorb more heat from sunlight, trapping warmth and making them ideal for cold conditions.
