Unit of Heat – Class 11 | Chapter – 2 | Physics Short Notes Series PDF for NEET & JEE

Unit of HeatThe unit of heat is Joule (J), named after James Prescott Joule, who established the mechanical equivalent of heat. However, the calorie (cal) is another common unit of heat, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius at standard atmospheric pressure. One calorie is equivalent to approximately 4.184 joules.

What is Temperature?

Temperature is a measure of the degree of hotness or coldness of an object or a substance. It is a physical quantity that expresses the average kinetic energy of the particles in a substance, which is related to the sensation of warmth or coldness that we feel.

Temperature is typically measured using a thermometer, which contains a temperature-sensitive material that expands or contracts as the temperature changes. The most commonly used temperature scales are Celsius (°C), Fahrenheit (°F), and Kelvin (K). Celsius and Fahrenheit scales are based on the freezing and boiling points of water at standard atmospheric pressure, while the Kelvin scale is based on the absolute zero point of temperature (the theoretical temperature at which all substances would have zero kinetic energy).

Unit of Heat

Heat is represented by the symbol Q and the heat formula is given as;

Q = mCΔT


  • Q = heat
  • m = mass of the body
  • C = specific heat and
  • ΔT = temperature difference
Calorie 1 cal 4.184 J
Joules 1 J 0.000239006 kcal / 0.000947817Btu
BTU 1 Btu 1055.06 J

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By Team Learning Mantras