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Physics XI Notes for Physics Notes

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Heat Capacity And Specific Heat Capacity

Many experiments suggested that the amount of heat energy required to raise the temperature of a substance is directly proportional to:

  1. mass (m)
  2. Change in temperature (∆θ)

This can be expressed as,
Q = ms∆θ è1
Where, s is proportionality constant which is called specific heat capacity. Its value depends on the nature of the substance.

If ∆θ = 10C
Therefore,
Q = ms
This quantity of heat is called heat capacity or thermal capacity of a substance. It is defined as the amount of energy required to change the temperature of mass of the substance through 10C. its unit is called J/K in SI and calorie per Kelvin in CGS.

Again from equation 1
s = Q/m∆θ
if m = 1 unit
∆θ = 1 unit
Then,
s = Q
So, the specific heat capacity of a substance is defined as the amount of heat energy required to change the temperature of unit mass through 10C. Its SI unit is J/kg0C.

For water,
S = 4200 J/kg0K (SI)
= 1 calg-1K-1

For ice,
S = 2100 J/kg0K
= 0.5 calg-1K-1

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