Heat Transfer (3151909) MCQs

MCQs of Radiation

Showing 1 to 10 out of 27 Questions
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1.

heat transfer by radiation mainly depends upon

(a)

its temperature
(b)

nature of the body
(c)

its surface properties
(d)

all of the above
Answer:

Option (d)

2.

According to Stefan-Boltzmann law, ideal radiators emit energy at a rate proportional to 

(a)

absolute temperature
(b)

square of temperature
(c)

the fourth power of absolute temperature
(d)

fifth power of temperature
Answer:

Option (c)

3.

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.

(a)

equal to
(b)

directly proportional to
(c)

inversely proportional to
(d)

none of the above
Answer:

Option (b)

4.

A radiator in a domestic heating system operates at a surface temperature of 60 degree Celsius. Calculate the heat flux at the surface of the radiator if it behaves as a black body

(a)

697.2 W/m2
(b)

786.9 W/m2
(c)

324.7 W/m2
(d)

592.1 W/m2
Answer:

Option (a)

5.

During a cold winter season, a person prefers to sit near a fire. Which of the following modes of heat transfer provides him the maximum heat?

(a)

Conduction from the fire
(b)

If it is near the fire, convection sounds good
(c)

Convection and radiation together
(d)

Radiation will provide quick warmth
Answer:

Option (d)

6.

The value of transmissivity may vary from

(a)

0-1
(b)

1-2
(c)

3-4
(d)

4-5
Answer:

Option (a)

7.

 A cavity with a small hole will always behave as a

(a)

White body
(b)

Transparent body
(c)

Black body
(d)

Opaque body
Answer:

Option (c)

8.

Transmissivity is defined as

(a)

The fraction of total energy transmitted by the body
(b)

The fraction of total energy reflected by the body
(c)

The fraction of total energy absorbed by the body
(d)

The fraction of total energy absorbed and radiated by the body
Answer:

Option (a)

9.

Reflectivity is defined as

(a)

The fraction of total energy transmitted by the body
(b)

The fraction of energy reflected by the body
(c)

The fraction of total energy absorbed by the body
(d)

The fraction of total energy absorbed and radiated by the body
Answer:

Option (b)

10.

Which one is true for an opaque body?

(a)

Transmissivity is zero
(b)

Reflectivity is zero
(c)

Absorptivity is zero
(d)

Reflectivity is unity
Answer:

Option (a)

Showing 1 to 10 out of 27 Questions
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