MCQ Detailed View

Heat is a form of energy transfer that moves from a hotter object to a cooler one due to a difference in temperature. In physics, every type of energy has a standard measurement unit defined by the International System of Units (SI). The SI unit of heat is the Joule (J) because heat is a type of energy.

A joule is defined as the amount of energy transferred when a force of one newton moves an object one meter in the direction of the force. Heat, like other forms of energy such as mechanical work or electrical energy, is measured in joules because it represents energy flow between bodies.

Historically, heat was measured in calories. One calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1°C. However, in the SI system, calories have been replaced by joules for standardization. 1 calorie equals approximately 4.186 joules.

Other options in this question are incorrect because:

• 
  

  Watt (W): Measures the rate of energy transfer (power), not heat itself.

  
  


• 
  

  Volt (V): Measures electric potential difference.

  
  


• 
  

  Newton (N): Measures force.

  
  

The correct choice is Joule, as it represents the energy transferred as heat. This aligns with the law of conservation of energy, which treats heat as another form of energy.

Understanding that heat is energy is essential in thermodynamics, a branch of physics that explains energy transfer, work, and temperature changes. Many practical applications, such as engine efficiency, heating systems, and chemical reactions, are based on energy measured in joules.

Thus, the SI unit of heat is Joule (J), making option C the correct answer.