# Practice Test: Question Set - 01

**1. Unit of thermal conductivity in M.K.S. units is**

- (A) K cal/kg m² °C

- (B) K cal m/hr m² °C

- (C) K cal/hr m² °C

- (D) K calm/hr °C

**2. Thermal diffusivity is a**

- (A) Function
of temperature

- (B) Physical
property of a substance

- (C) Dimensionless
parameter

- (D) All
of these

**3. Unit of thermal conductivity in S.I. units is**

- (A) J/m² sec

- (B) J/m °K sec

- (C) W/m °K

- (D) Option (B) and (C) above.

**4. Which of the following statement is wrong?**

- (A) The heat
transfer in liquid and gases takes place according to convection

- (B) The amount
of heat flow through a body is dependent upon the material of the body

- (C) The thermal
conductivity of solid metals increases with rise in temperature

- (D) Logarithmic
mean temperature difference is not equal to the arithmetic mean temperature
difference

**5. Thermal conductivity of solid metals with rise in temperature normally**

- (A) Increases

- (B) Decreases

- (C) Remain constant

- (D) May increase or decrease depending on
temperature

**6. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the**

- (A) Reynold's
number

- (B) Grashoff's
number

- (C) Reynold's
number, Grashoff's number

- (D) Prandtl
number, Grashoff's number

**7. Thermal conductivity of non-metallic amorphous solids with decrease in temperature**

- (A) Increases

- (B) Decreases

- (C) Remain constant

- (D) May increase or
decrease depending on temperature

**8. According to Dalton's law of partial pressures, (where**

*p*= Barometric pressure,_{b}*p*= Partial pressure of dry air, and_{a }*p*= Partial pressure of water vapour)_{v}

_{}- (A)

*P*=

_{b}*p*

_{a}- p_{v}- (B)

*P*=

_{b}*p*+

_{a}*p*

_{v}- (C)

*P*

_{b}*= p*

_{a }× p_{v}- (D)

*P*=

_{b}*p*/

_{a}*p*

_{v}**9. Heat transfer takes place as per**

- (A) Zeroth law of
thermodynamics

- (B) First law of
thermodynamic

- (C) Second law of the
thermodynamics

- (D) Kirchoff's law

**10. The heat transfer by conduction through a thick sphere is given by**

- (A)

*Q =*2

*πkr*

_{1}r_{2}(T_{1}- T_{2})/ (r_{2}- r_{1})- (B)

*Q =*4

*πkr*

_{1}r_{2}(T_{1}- T_{2})/ (r_{2}- r_{1})- (C)

*Q =*6

*πkr*

_{1}r_{2}(T_{1}- T_{2})/ (r_{2}- r_{1})- (D)

*Q =*8

*πkr*

_{1}r_{2}(T_{1}- T_{2})/ (r_{2}- r_{1})**11. When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by**

- (A) Conduction

- (B) Convection

- (C) Radiation

- (D) Conduction and
convection

**12. Fourier's law of heat conduction is (where**

*Q*= Amount of heat flow through the body in unit time,*A*= Surface area of heat flow, taken at right angles to the direction of heat flow,*dT*= Temperature difference on the two faces of the body,*dx*= Thickness of the body, through which the heat flows, taken along the direction of heat flow, and*k*= Thermal conductivity of the body)- (A)

*k. A. (dT/dx)*

- (B)

*k. A. (dx/dT)*

- (C)

*k. (dT/dx)*

- (D)

*k. (dx/dT)*

**13. When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by**

- (A) Conduction

- (B) Convection

- (C) Radiation

- (D) Conduction and
convection

**14. Reynolds number (**

*R*) is given by (where_{N}*h*= Film coefficient,*l*= Linear dimension,*V*= Velocity of fluid,*k*= Thermal conductivity,*t*= Temperature, ρ = Density of fluid,*c*= Specific heat at constant pressure, and μ = Coefficient of absolute viscosity)_{p}- (A)

*R*

_{N}= hl/k- (B)

*R*

_{N}=*μ c*

_{p}/k- (C)

*R*

_{N}=*ρ V l /μ*

- (D)

*R*

_{N}= V²/t.c_{p }**15. Sensible heat is the heat required to**

- (A) Change vapour into
liquid

- (B) Change liquid into
vapour

- (C) Increase the
temperature of a liquid of vapour

- (D) Convert water
into steam and superheat it

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