MCQ Detailed View

The concept of heat capacity is fundamental in thermodynamics. The heat required to raise the temperature of a body by 1 K is known as thermal capacity or simply heat capacity. It is an extensive property, meaning it depends on the total amount of substance present.

Mathematically, thermal capacity is expressed as:

C=QΔTC = \dfrac{Q}{\Delta T}C=ΔTQ

where Q is the heat absorbed or released by the body, and ΔT is the change in temperature. The unit of thermal capacity in the SI system is joule per kelvin (J K⁻¹).

It is important to distinguish between thermal capacity and specific heat capacity. Specific heat capacity refers to the amount of heat required to raise the temperature of 1 kilogram of a substance by 1 K. On the other hand, thermal capacity refers to the heat required to raise the temperature of the entire body by 1 K, regardless of its mass. The relation between them is:

$$C=m\cdot c$$

where m is the mass of the body, and c is the specific heat capacity of the material.

For example, if a block of copper has a mass of 2 kg and the specific heat capacity of copper is 385 J kg⁻¹ K⁻¹, then its thermal capacity is:

C=2×385=770 JK−1C = 2 \times 385 = 770 \, J K⁻¹C=2×385=770JK−1

This means 770 joules of heat are required to increase the temperature of the copper block by 1 K.

Other terms in the options:

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  Specific heat is related but defined per unit mass.

  
  


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  Water equivalent is a concept used in calorimetry, representing the mass of water that absorbs the same amount of heat as the body for a given temperature rise.

  
  


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  “None of the above” is incorrect since thermal capacity is the accepted term.

  
  

Thus, the correct answer is thermal capacity, which directly measures the heat required to change a body’s temperature by one kelvin.