Mechanical Engineering Archives

Question: According to Stefan’s law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.
[A].

Correct

[B].

Incorrect

Answer: Option A

Explanation:

No answer description available for this question.

According to Stefan’s law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature. Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

Kirchhoff’s law states that

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Question: Kirchhoff’s law states that
[A].

the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature

[B].

the wave length corresponding to the maximum energy is proportional to the absolute temperature

[C].

the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body

[D].

none of the above

Answer: Option C

Explanation:

No answer description available for this question.

Kirchhoff’s law states that Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

According to Prevost’s theory of exchanges, every body irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies.

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Question: According to Prevost’s theory of exchanges, every body irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies.
[A].

True

[B].

False

Answer: Option A

Explanation:

No answer description available for this question.

According to Prevost’s theory of exchanges, every body irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies. Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0.

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Question: For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0.
[A].

Correct

[B].

Incorrect

Answer: Option A

Explanation:

No answer description available for this question.

For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0. Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning / admin

Question: An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by
[A].

[B].

[C].

e1 + e2

[D].

e1e2

Answer: Option A

Explanation:

No answer description available for this question.

An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.

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Question: A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.
[A].

True

[B].

False

Answer: Option A

Explanation:

No answer description available for this question.

A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray. Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

Emissivity of a body will be equal to its absorptivity at all temperatures.

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Question: Emissivity of a body will be equal to its absorptivity at all temperatures.
[A].

Yes

[B].

Answer: Option B

Explanation:

No answer description available for this question.

Emissivity of a body will be equal to its absorptivity at all temperatures. Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning / admin

Question: If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called
[A].

absorptive power

[B].

emissive power

[C].

emissivity

[D].

none of these

Answer: Option B

Explanation:

No answer description available for this question.

If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning