What is Heat in Physics? | Definition, Formula, Types, Units – Thermometry and Calorimetry

Heat Definition Physics:
The definition of heat is a form of energy that causes a difference in temperature, or the perception of warmth. An example of heat is hot water.

We are giving a detailed and clear sheet on all Physics Notes that are very useful to understand the Basic Physics Concepts.

What is Heat in Physics? | Definition, Formula, Types, Units – Thermometry and Calorimetry

Heat is a form of energy called thermal energy which flows from a (hotter) higher temperature body to a lower temperature body (colder) when they are placed in contact.

Heat or thermal energy of a body is the sum of kinetic energies of all its constituent particles, on account of translational, vibrational and rotational motion.

Types of Heat Transfer:
Heat is transfered via

  • Solid material (conduction)
  • Liquids and gases (convection) and
  • Electromagnetic waves (radiation).

Heat Formula in Thermodynamics:
The equation for calculating heat energy is

Q = mCpΔT

Q is the heat variable, (cal or J)
m is the mass of the object,
Cp is the specific heat constant and (J/g)
ΔT is the temperature change.

Heat Units Physics:
The SI unit of heat energy is joule (J).
The practical unit of heat energy is calorie.

1 cal = 4.18 J

1 calorie is the quantity of heat required to raise the temperature of 1 g of water by 1°C (from 14.5°C to 15.5°C).

Mechanical energy or work (W) can be converted into heat (Q) by

W = JQ

J = Joule’s mechanical equivalent of heat.
J is a conversion factor (not a physical quantity) and its value is 4.186 J/cal.

Thermometry and Calorimetry:
The thermometer is a device used to check the temperature of an object. This branch of measurement of the temperature of a substance is called thermometry. It is measured in degrees or Fahrenheit, usually.

Calorimetry also means the measurement of heat but in joules. It states the amount of heat lost by the body is the amount of heat gained by its surrounding.

Heat Energy Temperature and its Measurement
Thermometric Property Thermometers
Thermal Expansion Thermal Equilibrium
Triple Point of Water Specific Heat Capacity
Thermal Capacity Water Equivalent
Latent Heat Joule’s Law