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Free download in PDF Heat Objective Type Questions & Answers for competitive exams. These objective type questions are very important for competitive exams like IIT-JEE, NEET, AIIMS, JIPMER etc. These short solved questions or quizzes are provided by Gkseries.
(21)
Metals are good conductors of heat because
[A]
their atoms collide frequently
[B]
their atoms-are relatively far apart
[C]
they contain free electrons
[D]
they have high density
Answer: their atoms collide frequently
(22)
Total heat is the heat required to
[A]
change vapour into liquid
[B]
change liquid into vapour
[C]
increase the temperature of a liquid or vapour
[D]
convert water into steam and superheat it
Answer: convert water into steam and superheat it
(23)
Thermal conductivity of water at 20°C is of the order of
[A]
0.1
[B]
0.23
[C]
0.42
[D]
0.51
(24)
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]
determined by the time taken to reach 100°C from 0°C
Answer: the time taken to attain 63.2% of the value of initial temperature difference
(25)
Heat flows from one body to other when they have
[A]
different heat contents
[B]
different specific heat
[C]
different atomic structure
[D]
different temperatures
Answer: different temperatures
(26)
In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by
[A]
hr (time)
[B]
sqm (area)
[C]
°C (temperature)
[D]
cm (thickness)
(27)
Which of the following has least value of conductivity
[A]
glass
[B]
water
[C]
plastic
[D]
air
(28)
Which of the following is expected to have highest thermal conductivity
[A]
steam
[B]
solid ice
[C]
melting ice
[D]
water
(29)
Thermal conductivity of glass-wool varies from sample to sample because of variation in
[A]
composition
[B]
density
[C]
porosity
[D]
all of the above
Answer: all of the above.
(30)
Which of the following has maximum value of thermal conductivity
[A]
aluminium
[B]
steel
[C]
brass
[D]
copper
31
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]
a vapour seal
32
The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj - 2K2 will be
[A]
I
[B]
0.5
[C]
2
[D]
0.25
33
Thermal diffusivity is
[A]
a dimensionless parameter
[B]
function of temperature
[C]
used as mathematical model
[D]
a physical property of the material
Answer: a physical property of the material
34
Unit of thermal diffusivity is
[A]
m2/hr
[B]
m2/hr°C
[C]
kcal/m2 hr
[D]
kcal/m.hr°C
35
Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called
[A]
thermal resistance
[B]
thermal coefficient
[C]
temperature gradient
[D]
thermal conductivity
Answer: thermal conductivity
36
A grey body is one whose absorptivity
[A]
varies with temperature
[B]
varies with wavelength of the incident ray
[C]
is equal to its emissivity
[D]
does not vary with temperature and. wavelength of the incident ray
Answer: is equal to its emissivity
37
A non-dimensional number generally associated with natural convection heat transfer is
[A]
Grashoff number
[B]
Nusselt number
[C]
Weber number
[D]
Prandtl number
38
In counter flow heat exchangers
[A]
both the fluids at inlet (of heat ex¬changer where hot fluid enters) are in their coldest state
[B]
both the fluids at inlet are in their hot¬test state
[C]
both the fluids .at exit are in their hottest state
[D]
one fluid is in hottest state and other in coldest state at inlet
Answer: both the fluids at inlet are in their hot¬test state
39
Fourier's law of heat conduction is valid for
[A]
one dimensional cases only
[B]
two dimensional cases only
[C]
three dimensional cases only
[D]
regular surfaces having non-uniform temperature gradients
Answer: one dimensional cases only
40
All radiations in a black body are
[A]
reflected
[B]
refracted
[C]
transmitted
[D]
absorbed
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