(i) R = = =
Greater the K, smaller will be the thermal resistance.
(ii) Unit of R = =
(iii) Dimensions of R = .
Where = dimensions of kelvin temperature.
= .
Note: K denotes thermal conductivity of material , denotes dimensions of keliven temperature. is chosen to avoid confusion between conductivity-coefficient and kelvin temperature.
(i) This quantity is respectively by h.
h =
h = = where
= density of material , s = specific heat of material
K = coefficient of thermal conductivity
(ii) Unit of h = .
(iii) Dimensions of h =
= =
= .
Ingen Hausz experiments/apparatus:
Several rods are coated with wax.
K = thermal conductivity of material of rod.
l = length of rod upto which wax melts.
= constant.
= = =
(i) t = time taken, x = thickness of ice formed
= density of ice, L = latent heat of ice
K = coefficient of thermal conducitivity
= temperature above lake
t =
(iii) t =
= time taken in increasing thickness of ice from to .
It is the process in which transmission of heat occurs in the form of electromagnetic waves of wavelength from about 8000 Å to about 4 mm. Intervening medium is not required for radiation. Heat radiations are actually covered under infrared waves. In vacuum, the speed of radiation is m/s. This is equal to velocity of light or velocity of electromagnetic radiations.
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