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1. A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between the body and that of the surroundings is T, then (a) Both spheres will cool at the same rate for small values of T (b) Both spheres will cool at the same rate for large values of T (c) The hollow sphere will cool at a faster rate for all the values of T (d) The solid sphere will cool a faster rate for all the values of T 2. Upto the critical radius of insulation: (a) Added insulation increases heat loss (b) Added insulation decreases heat loss (c) Convection heat loss is less than conduction heat loss (d) Heat flux decreases 3. Which one of the following is correct? Fins are used to increase the heat transfer from a surface by: (a) Increasing the temperature difference (b) Increasing the effective surface area (c) Increasing the convective heat transfer coefficient (d) None of the above

1. A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between the body and that of the surroundings is T, then (a) Both spheres will cool at the same rate for small values of T (b) Both spheres will cool at the same rate for large values of T (c) The hollow sphere will cool at a faster rate for all the values of T (d) The solid sphere will cool a faster rate for all the values of T 2. Upto the critical radius of insulation: (a) Added insulation increases heat loss (b) Added insulation decreases heat loss (c) Convection heat loss is less than conduction heat loss (d) Heat flux decreases 3. Which one of the following is correct? Fins are used to increase the heat transfer from a surface by: (a) Increasing the temperature difference (b) Increasing the effective surface area (c) Increasing the convective heat transfer coefficient (d) None of the above

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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1. A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between the body and that of the surroundings is T, then (a) Both spheres will cool at the same rate for small values of T (b) Both spheres will cool at the same rate for large values of T (c) The hollow sphere will cool at a faster rate for all the values of T (d) The solid sphere will cool a faster rate for all the values of T 2. Upto the critical radius of insulation: (a) Added insulation increases heat loss (b) Added insulation decreases heat loss (c) Convection heat loss is less than conduction heat loss (d) Heat flux decreases 3. Which one of the following is correct? Fins are used to increase the heat transfer from a surface by: (a) Increasing the temperature difference (b) Increasing the effective surface area (c) Increasing the convective heat transfer coefficient (d) None of the above 4. Which one of the following numbers represents the ratio of kinematic viscosity to the thermal diffusivity? (a) Grashoff number (b) Prandtl number (c) Biot number (d) Nusselt number 5. In radiative heat transfer, a grey surface is one: (a) Which appears grey to the eye Whose emissivity is independent of wavelength (b) (c) Which has reflectivity equal to zero (d) Which appears equally bright from all directions.
Transcribed Image Text:1. A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between the body and that of the surroundings is T, then (a) Both spheres will cool at the same rate for small values of T (b) Both spheres will cool at the same rate for large values of T (c) The hollow sphere will cool at a faster rate for all the values of T (d) The solid sphere will cool a faster rate for all the values of T 2. Upto the critical radius of insulation: (a) Added insulation increases heat loss (b) Added insulation decreases heat loss (c) Convection heat loss is less than conduction heat loss (d) Heat flux decreases 3. Which one of the following is correct? Fins are used to increase the heat transfer from a surface by: (a) Increasing the temperature difference (b) Increasing the effective surface area (c) Increasing the convective heat transfer coefficient (d) None of the above 4. Which one of the following numbers represents the ratio of kinematic viscosity to the thermal diffusivity? (a) Grashoff number (b) Prandtl number (c) Biot number (d) Nusselt number 5. In radiative heat transfer, a grey surface is one: (a) Which appears grey to the eye Whose emissivity is independent of wavelength (b) (c) Which has reflectivity equal to zero (d) Which appears equally bright from all directions.
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