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Heat Radiation Online Exam Quiz

Important questions about Heat Radiation. Heat Radiation MCQ questions with answers. Heat Radiation exam questions and answers for students and interviews.

The value of transmissivity may vary from

Options

A : a. 0-1

B : b. 1-2

C : c. 3-4

D : d. 4-5

Of the radiant energy 350W/m² incident upon a surface 250W/m² is absorbed, 60W/m² is reflected and the remainder is transmitted through the surface. Workout the value for absorptivity for the surface material

Options

A : a. 0.113

B : b. 0.114

C : c. 0.115

D : d. 0.116

“Transmissivity can also be defined as ratio of transmitted radiation to that of incident energy flow”. True or false

Options

A : a. True

B : b. False

C : c. May be

D : d. Can't say

A cavity with a small hole will always behave as a

Options

A : a. White body

B : b. Transparent body

C : c. Black body

D : d. Opaque body

What is the wavelength band of gamma rays?

Options

A : a. 1 * 10¯? to 4 * 10¯? micron meter

B : b. 2 * 10¯? to 2.4 * 10¯? micron meter

C : c. 3 * 10¯? to 3.4 * 10¯? micron meter

D : d. 4 * 10¯? to 1.4 * 10¯? micron meter

Transmissivity is defined as

Options

A : a. Fraction of total energy transmitted by the body

B : b. Fraction of total energy reflected by the body

C : c. Fraction of total energy absorbed by the body

D : d. Fraction of total energy absorbed and radiated by the body

A polished metal pipe 5 cm outside diameter and 370 K temperature at the outer surface is exposed to ambient conditions at 295 K temperature. The emissivity of the surface is 0.2 and the convection coefficient of heat transfer is 11.35 W/m² degree. Calculate the overall coefficient of heat transfer by the combined mode of convection and radiation

Options

A : a. 11.04 W/m² degree

B : b. 12.04 W/m² degree

C : c. 13.04 W/m² degree

D : d. 14.04 W/m² degree

Radiant energy with an intensity of 800 W/m² strikes a flat plate normally. The absorptivity is thrice the reflectivity and twice the transmissivity. Determine the rate of transmission

Options

A : a. 155.47 W/m²

B : b. 145.47 W/m²

C : c. 135.47 W/m²

D : d. 125.47 W/m²

With respect to incident radiation, transmissivity varies with

Options

A : a. Time

B : b. Temperature

C : c. Surface area

D : d. Wavelength

A body through which all the incident radiations passes, is called

Options

A : a. Opaque body

B : b. Black body

C : c. Transparent body

D : d. White body

Reflectivity is defined as

Options

A : a. Fraction of total energy transmitted by the body

B : b. Fraction of energy reflected by the body

C : c. Fraction of total energy absorbed by the body

D : d. Fraction of total energy absorbed and radiated by the body

A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its face receives radiant energy from a heat source at the rate of 2 W. If heat transfer coefficient on both surfaces of the plate is stated to be 87.5 W/m 2 K, workout the energy lost by reflection

Options

A : a. 0.8 W

B : b. 0.3 W

C : c. 0.9 W

D : d. 0.10 W

The value of reflectivity depends upon (i) Body temperature (ii) Wavelength of reflected radiation (iii) Nature of surface of body Identify the correct statement

Options

A : a. 1 and 2

B : b. 2 and 3

C : c. 2 only

D : d. 1 and 3

When a surface absorbs a certain fixed percentage of striking radiation the surface is called

Options

A : a. Grey body

B : b. Black body

C : c. White body

D : d. Opaque body

Which one is true regarding gases?

Options

A : a. Reflectivity is unity

B : b. Absorptivity is zero

C : c. Reflectivity is zero

D : d. Transmissivity is zero

Thin glass plate is an example of

Options

A : a. Transparent body

B : b. Opaque body

C : c. Black body

D : d. White body

Which one is true for opaque body?

Options

A : a. Transmissivity is zero

B : b. Reflectivity is zero

C : c. Absorptivity is zero

D : d. Reflectivity is unity

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of transmission

Options

A : a. 236.74 W/m²

B : b. 116.37 W/m²

C : c. 187.87 W/m²

D : d. 456.09 W/m²

The absorptivity of a surface depends upon (i) Direction of reflected radiation (ii) Temperature of the surface (iii) Composition Identify the correct statements

Options

A : a. 1, 2 and 3

B : b. 1 and 3

C : c. 2 only

D : d. 2 and 3

What is the absorptivity of gray body?

Options

A : a. Below unity

B : b. Unity

C : c. 2

D : d. 2.5

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