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Mechanical Engineering :: Heat and Mass Transfer

  1. The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

  2. A.

     Move actually

    B.

     Do not move actually

    C.

     Affect the intervening medium

    D.

     Does not affect the intervening medium

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  3. The thermal diffusivities for solids are generally

  4. A.

     Less than those for gases

    B.

     Less than those for liquids

    C.

     More than those for liquids and gases

    D.

     More or less same as for liquids and gases

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  5. Heat transfer by radiation mainly depends upon

  6. A.

     Its temperature

    B.

     Nature of the body

    C.

     Kind and extent of its surface

    D.

     All of the above

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  7. The transfer of heat by molecular collision is known as

  8. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     None of these

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  9. According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a

  10. A.

     Grey body

    B.

     Brilliant white polished body

    C.

     Red hot body

    D.

     Black body

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  11. 40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

  12. A.

     0.45

    B.

     0.55

    C.

     0.40

    D.

     0.75

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  13. The heat transfer takes place according to

  14. A.

     Zeroth law of thermodynamics

    B.

     First law of thermodynamics

    C.

     Second law of thermodynamics

    D.

     Kirchhoff's law

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  15. In case of liquids and gases, the heat transfer takes place according to

  16. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     None of these

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  17. Depending on the radiating properties, a body will be opaque when

  18. A.

     P = 0, x = 0 and a = 1

    B.

     P=1, x = 0 and a = 0

    C.

     P = 0, x = 1 and a = 0

    D.

     X = 0, a + p = 1

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  19. Log mean temperature difference in case of counter flow compared to parallel flow will be

  20. A.

     Same

    B.

     More

    C.

     Less

    D.

     Depends on other factors

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