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Heat Definition

The movement of kinetic energy from one medium to another is known as heat. The direction of heat energy transfer is from a substance with a higher temperature to a substance with a lower temperature because faster-vibrating molecules pass their energy to slower-vibrating molecules. The vibrational energy is often referred to as heat content. Heat's SI unit is Joule.

Heat Definition

Heat Classification

Heat is classified into two categories that are hot and cold.

1. Hot

Things are considered hot if they contain a lot of heat. Some examples of hot objects are the sun, fire, hot pans, hot air from a hairdryer, lava from volcanic eruptions, and other hot things in our environment.

2. Cold

Cold items are those that contain less heat. Examples of cold items include ice, air from an air conditioner, cold beverages, etc.

Heat Transfer Mechanisms

Heat is not a physical thing but a type of energy. Heat doesn't have mass. Heat can transfer from one medium to another by conduction, convection, and radiation.

1. Conduction

Conduction is a method of transporting heat. Heat is transferred through contact in conduction. The method by which heat is transmitted from an item's hot end to its cold end is known as conduction.

2. Convection

Convection is the method of transferring heat. Convection is the process in which fluid movement transfers heat from one point to another.

3. Radiation

Radiation is the method of transferring heat. Radiation is the process in which heat transfer through electromagnetic waves without using particles.

Advantages and Disadvantages of Heat Energy


  1. Heat is easily converted to electrical energy.
  2. Heat is a renewable energy source, as there are numerous ways to generate it.
  3. Cooking, baking, heating, and other processes utilize thermal energy.


  1. Continuous greenhouse gas emissions badly damage nature.
  2. Thermal power plants emit steam and heat, negatively impacting climate.

Heat Energy Applications

  1. Several firms use this energy.
  2. It is utilized for cooking and ironing.
  3. To develop automobile engines.
  4. Heat is used in incinerators to burn garbage.
  5. It is regularly used in bakeries.
  6. In a thermal power plant, heat is converted into energy.

FAQ on Heat

1. Differences between convection, radiation, and conduction.


Sr. No Conduction Convection Radiation
1 In conduction, heat is transferred between things by direct contact. In convection, heat is transferred within the fluid. Radiation is the method in which heat transfer through electromagnetic waves without using particles.
2 It doesn't follow the law of refraction and reflection. It doesn't follow the law of refraction and reflection. It follows the law of refraction and reflection.
3 Conduction transfer heat slowly. Convection transfer heat quickly. Radiation transfer heat quickly.
4 Heat is transferred through a solid hot object. Intermediate objects transfer heat. For, e.g. the transfer of heat between air and water. Heat is transferred via radiation using electromagnetic waves.
5 In conduction, heat transmission occurs because of the temperature difference. In convention, heat transmission occurs because of the difference in densities. Heat transmission occurs in objects that have a temperature higher than 0 K.

2. List out primary sources of heat.

Answer: Primary sources of heat are:

  1. Sun
  2. Chemical
  3. Electrical
  4. Nuclear

3. What is the unit of heat transfer?


  1. SI unit: Joule
  2. MKS unit: Cal
  3. Rate of heat transfer: KW

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