Q. The value of Lorenz number in 10¯⁸ W ohms/K² is

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Q. Consider the following parameters
(i) Composition
(ii) Density
(iii) Porosity
(iv) Structure
Then, thermal conductivity of glass wool varies from sample to sample because of variation is

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Q. The thermal conductivity and the electrical conductivity of a metal at absolute temperature are related as

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Q. The relation Ϫ² t =0 is referred to as

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Q. The unit of thermal diffusivity is

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Q. To effect a bond between two metal plates, 2.5 cm and 15 cm thick, heat is uniformly applied through the thinner plate by a radiant heat source. The bonding must be held at 320 K for a short time. When the heat source is adjusted to have a steady value of 43.5 k W/m², a thermocouple installed on the side of the thinner plate next to source indicates a temperature of 345 K. Calculate the temperature gradient for heat conduction through thinner plate. In the diagram, the upper plate is 2.5 cm thick while the lower is 15 cm thick.

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Q. The diffusion equations
Ɏ²t + q g = (1/α) (d t/d r)
Governs the temperature distribution under unsteady heat flow through a homogenous and isotropic material. The Fourier equation follows from this expression when

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Q. The famous Fourier series is named after

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Q. Fourier law of heat conduction is best represented by

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Q. Here are some assumptions that are made for Fourier law. Identify the wrong one

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Q. Consider the following statements:

The Fourier heat conduction equation

Q = -k A d t /d x

Presumes

i) Steady state conditions

ii) Constant value of thermal conductivity

iii) Uniform temperature at the wall surface

iv) One dimensional heat flow

Which of these statements are correct?

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Q. Negative sign in Fourier heat conduction equation indicates

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Q. Transmission of heat i.e. molecular is smallest in case of

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Q. Which one is not the unit of thermal conductivity?

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Q. “Thermal conductivity represents the amount of heat conducted across unit area when a temperature difference of one kelvin”. True or false

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Q. Which of the following is the unit of thermal resistance?

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Q. Thermal conductivity is defined as the heat flow per unit time

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Q. Mark the matter with least value of thermal conductivity

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Q. Which one of the following forms of water have the highest value of thermal conductivity?

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Q. The average thermal conductivities of water and air conform to the ratio

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