According to Wien's law, the wavelength corresponding to maximum energy is proportion to
Absolute temperature (T)
I²
F
T
Correct Answer :
A. Absolute temperature (T)
Related Questions
The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
Stanton number
Biot number
Peclet number
Grashoff number
The concept of overall coefficient of heat transfer is used in heat transfer problems of
Conduction
Convection
Radiation
Conduction and convection
The transfer of heat by molecular collision is known as
Conduction
Convection
Radiation
None of these
A non-dimensional number generally associated with natural convection heat transfer is
Grashoff number
Nusselt number
Weber number
Prandtl number
Thermal conductivity of air with rise in temperature
Increases
Decreases
Remain constant
May increase or decrease depending on temperature
The highest thermal diffusivity is of
Iron
Lead
Concrete
Wood
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a
Black body
Grey body
Opaque body
White body
The amount of radiation mainly depends on
Nature of body
Temperature of body
Type of surface of body
All of the above
According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the
Absolute temperature
Square of the absolute temperature
Cube of the absolute temperature
Fourth power of the absolute temperature
Joule sec is the unit of
Universal gas constant
Kinematic viscosity
Thermal conductivity
Planck's constant
A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is
h₁ + h₂ + h₃
(h₁.h₂.h₃)1/3
1/h₁ + 1/h₂ + 1/h₃
None of these
Thermal diffusivity is
A dimensionless parameter
Function of temperature
Used as mathematical model
A physical property of the material
The unit of overall coefficient of heat transfer is
kcal/m²
kcal/hr °C
kcal/m² hr °C
kcal/m hr °C
Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of
1 : 1
2 : 1
1 : 2
4 : 1
Conduction is a process of heat transfer
From one particle of the body to another without the actual motion of the particles
From one particle of the body to another by the actual motion of the heated particles
From a hot body to a cold body, in a straight line, without affecting the intervening medium
None of the above
The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.
Equal to
Directly proportional to
Inversely proportional to
None of these
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
Conduction
Convection
Radiation
Conduction and convection
According to Wien's law, the wavelength corresponding to maximum energy is proportion to
Absolute temperature (T)
I²
F
T
In a shell and tube heat exchanger, baffles are provided on the shell side to
Improve heat transfer
Provide support for tubes
Prevent stagnation of shell side fluid
All of these
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
Absorptive power
Emissive power
Emissivity
None of these
The value of Prandtl number for air is about
0.1
0.3
0.7
1.7
The amount of radiation mainly depends upon the
Nature of the body
Temperature of the body
Type of surface of the body
All of these
Which of the following statement is correct?
A grey body is one which absorbs all radiations incident on it.
At thermal equilibrium, the emissivity and absorptivity are same.
The energy absorbed by a body to the total energy falling on it, is called emissivity.
A perfect body is one which is black in colour.
Planck's law holds good for
Black bodies
Polished bodies
All coloured bodies
All of the above
The unit of Stefan Boltzmann constant is
Watt/cm² °K
Watt/cm4 °K
Watt²/cm °K⁴
Watt/cm² °K⁴
The ratio of the energy absorbed by the body to total energy falling on it is called
Absorptive power
Emissive power
Absorptivity
Emissivity
A composite slab has two layers of different materials with thermal conductivities k₁ and k₂. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be
k₁ k₂
(k₁ + k₂)
(k₁ + k₂)/ k₁ k₂
2 k₁ k₂/ (k₁ + k₂)
Heat transfer by radiation mainly depends upon
Its temperature
Nature of the body
Kind and extent of its surface
All of the above
The use of heat exchangers is made in
Radiators in automobile
Condensers and boilers in steam plants
Condensers and evaporators in refrigeration and air conditioning units
All of the above
According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
Absolute temperature
T²
T⁵
T