Engineering :: Heat Transfer

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221.

Radiation heats transfer between two surfaces can be reduced by

A.	Polishing the surface	B.	Bringing the surfaces closer together
C.	Preheating the surfaces closer together	D.	Introducing radiation shield between the surfaces

222.

Which of the following have the same units?

A.	Boltzmann constant and Planck's constant	B.	Stefan's canstant and Boltzmann constant
C.	Plank's constant and Stefan's constant	D.	Planck's constant and angular momentum

223.

Which of the following is wrong:

A.	Rough surfaces are better radiators than smooth surfaces	B.	Highly polished mirror like surfaces are very good radiators
C.	Black surfaces are better absorbers than white ones	D.	Black surfaces are better radiators than white ones

224.

The coefficient of linear expansion of a solid is L. The volume V of a cube of this solid on being heated by 1?C will change by

A.	VL	B.	3L
C.	3 VL	D.	VL/3

225.

Which of the following are generally diathermanous?

A.	Solids	B.	Liquids
C.	Gases	D.	All of the above

226.

Hydrogen cannot be liquefied at room temperature because

A.	it has low density	B.	it has high specific heat
C.	it is a diatomic gas	D.	its critical temperature is less than the room temperature

227.

A constant gas thermometer is based on

A.	Avogadro's law	B.	Graham's law
C.	Boyle's law	D.	Charle's law

228.

The temperature of sun can be measured using a

A.	standard thermometer	B.	radiation pyrometer
C.	platinum resistance thermometer	D.	mercury thermometer

229.

Which of the following can be used to measure a temperature around -50?C?

A.	Mercury thermometer	B.	Alcohol thermometer
C.	Thermocouple	D.	Platinum resistance thermometer

230.

A thin circulr disc has a concentric hole in it. On heating the diameter of hole will

A.	increase	B.	decrease
C.	remain constant