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Home » Engineering » Aptitude Test - 77
Hassan
1.Depending on the radiating properties, body will be transparent when (Where a = absorptivity, p = reflectivity, x = transmissivity)
A. P = 0, x = 0 and a = 1
B. P=1, x = 0, and a = 0
C. P = 0, T= 1, and a = 0
D. P = 0, x = 0 and a = 1
2.Thermal diffusivity of a substance is
A. Directly proportional to thermal conductivity
B. Inversely proportional to density of substance
C. Inversely proportional to specific heat
D. Directly proportional to thermal conductivity
3.Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature.
A. Minimum energy
B. Maximum energy
C. Both (A) and (B)
D. Minimum energy
4.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. This statement is known as
A. Kirchoff’s law
B. Stefan's law
C. Wien' law
D. Kirchoff’s law
5.Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.
A. Cold body to hot body
B. Hot body to cold body
C. Smaller body to larger body
D. Cold body to hot body
6. According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
A. Absolute temperature
B. T²
C. T⁵
D. Absolute temperature
7. For the hydrogen atom, which series describes electron transitions to the N=1 orbit, the lowest energy electron orbit? Is it the:
A. Lyman series
B. Balmer series
C. Paschen series
D. Lyman series
8. Total emissivity of polished silver compared to black body is
A. Same
B. Higher
C. More Or Less Same
D. Same
9.Stefan Boltzmann law is applicable for heat transfer by
A. conduction
B. convection
C. radiation
D. conduction
10.The thermal diffusivities for solids are generally
A. less than those for gases
B. jess than those for liquids
C. more than those for liquids and gases
D. less than those for gases
11.According to Stefan’s law, the total radiation from a black body per second per unit area is proportional to
A. absolute temperature
B. T2
C. T5
D. absolute temperature
12.The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit
A. Temperature
B. Thickness
C. Area
D. Temperature
13. The ratio of the energy absorbed by the body to total energy falling on it is called
A. Absorptive Power
B. Emissive Power
C. Absorptivity
D. Absorptive Power
14. The amount of radiation mainly depends on
A. nature of body
B. temperature of body
C. type of surface of body
D. nature of body
15.The emissive power of a body depends upon its
A. Temperature
B. Wave Length
C. Physical Nature
D. Temperature
16. In regenerator type heat exchanger, heat transfer takes place by
A. direct mixing of hot and cold fluids
B. a complete separation between hot and cold fluids
C. flow of hot and cold fluids alternately over a surface
D. direct mixing of hot and cold fluids
17.If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of
A. 3
B. 6
C. 9
D. 3
18.Absorptivity of a body will be equal to its emissivity
A. at all temperatures
B. at one particular temperature
C. when system is under thermal equi-librium
D. at all temperatures
19. Planck’s law holds good for
A. Black Bodies
B. Polished Bodies
C. All Coloured Bodies
D. Black Bodies
20. A grey body is one whose absorptivity
A. varies with temperature
B. varies with the wave length of incident ray
C. varies with both
D. varies with temperature
21. The time constant of a thermocouple is
A. the time taken to attain the final temperature to be measured
B. the time taken to attain 50% of the value of initial temperature difference
C. the time taken to attain 63.2% of the value of initial temperature difference
D. the time taken to attain the final temperature to be measured
22.The concept of overall coefficient of heat transfer is used in heat transfer problems of
A. conduction
B. convection
C. radiation
D. conduction
23.Thermal Conductivity Of Glass-Wool Varies From Sample To Sample Because Of Variation In
A. Composition
B. Density
C. Porosity
D. Composition
24. Moisture would find its way into insulation by vapour pressure unless it is prevented by
A. high thickness of insulation
B. high vapour pressure
C. less thermal conductivity insulator
D. high thickness of insulation
25. Thermal diffusivity is
A. a dimensionless parameter
B. function of temperature
C. used as mathematical model
D. a dimensionless parameter
26.Thermal diffusivity of a substance is .
A. proportional of thermal conductivity
B. inversely proportional to k
C. proportional to (k)
D. proportional of thermal conductivity
27. Thermal Conductivity Of Wood Depends On
A. Moisture
B. Density
C. Temperature
D. Moisture
28.Quilts and jackets keep us warm by
A. trapping air
B. preventing release of heat from our body
C. heating itself up
D. trapping air
29.By placing our hand above a hot object, we can feel heat because
A. it is releasing heat
B. our hand is releasing heat
C. our hand is cooling down
D. it is releasing heat
30.The objects that are cooler than other objects gain heat from
A. sun
B. surroundings
C. stove
D. sun
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