Questions and answers for exam Preparation

MCQs

Total Questions : 448 | Page 7 of 45 pages

Question 61. Temperature of steam at around 540°C can be measured by

Thermometer
Thermistor
Thermocouple
None of these

Discuss Question

Answer: Option C. -> Thermocouple

Question 62. The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.

Equal to
Directly proportional to
Inversely proportional to
None of these

Discuss Question

Answer: Option B. -> Directly proportional to

Question 63. The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

First law of thermodynamics
Newton's law of cooling
Newton's law of heating
Stefan's law

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Answer: Option B. -> Newton's law of cooling

Question 64. The use of heat exchangers is made in

Radiators in automobile
Condensers and boilers in steam plants
Condensers and evaporators in refrigeration and air conditioning units
All of the above

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Answer: Option D. -> All of the above

Question 65. Which of the following statement is wrong?

The heat transfer in liquid and gases takes place according to convection
The amount of heat flow through a body is dependent upon the material of the body
The thermal conductivity of solid metals increases with rise in temperature
Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference

Discuss Question

Answer: Option C. -> The thermal conductivity of solid metals increases with rise in temperature

Question 66. When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

α = 1, ρ = 0 and τ = 0
α = 0, ρ = 1 and τ = 0
α = 0, ρ = 0 and τ = 1
α + ρ = 1 and τ = 0

Discuss Question

Answer: Option C. -> α = 0, ρ = 0 and τ = 1

Question 67. Planck’s law holds good for

black bodies
polished bodies
all coloured bodies
all of the above

Discuss Question

Answer: Option A. -> black bodies

Question 68. Thermal conductivity of a material may be defined as the

Quantity of heat flowing in one second through one cm cube of material when opposite faces are maintained at a temperature difference of 1°C
Quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
All of the above

Discuss Question

Answer: Option D. -> All of the above

Question 69. A perfect black body is one which