What is the correct answer?

4

# 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

### Correct Answer :

B. Emissive power

### Related Questions

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4

# The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

First law of thermodynamics

Newton's law of cooling

Newton's law of heating

Stefan's law

What is the correct answer?

4

# A non-dimensional number generally associated with natural convection heat transfer is

Grashoff number

Nusselt number

Weber number

Prandtl number

What is the correct answer?

4

# Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

0.002

0.02

0.01

0.1

What is the correct answer?

4

# The natural convection air cooled condensers are used in

Domestic refrigerators

Water coolers

Room air conditioners

All of these

What is the correct answer?

4

# The heat transfer takes place according to

Zeroth law of thermodynamics

First law of thermodynamics

Second law of thermodynamics

Kirchhoff's law

What is the correct answer?

4

# In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

Parallel flow

Counter flow

Cross flow

All of these

What is the correct answer?

4

# The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

Temperature

Thickness

Area

Time

What is the correct answer?

4

# Which of the following is expected to have highest thermal conductivity?

Steam

Solid ice

Melting ice

Water

What is the correct answer?

4

# Depending on the radiating properties, a body will be black when

P = 0, x = 0 and a = 1

P= 1, T = 0 and a = 0

P = 0, x = 1 and a = 0

X = 0, a + p = 0 Where a = absorptivity, p = reflectivity, X = transmissivity.

What is the correct answer?

4

# Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

Cold body to hot body

Hot body to cold body

Smaller body to larger body

Larger body to smaller body

What is the correct answer?

4

# Thermal conductivity of water in general with rise in temperature

Increases

Decreases

Remain constant

May increase or decrease depending on temperature

What is the correct answer?

4

# LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is

Higher

Lower

Same

Depends on the area of heat exchanger

What is the correct answer?

4

# Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in

Electric heater

Steam condenser

Boiler

Refrigerator condenser coils

What is the correct answer?

4

# The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

Equal to one

Greater than one

Less than one

Equal to Nusselt number

What is the correct answer?

4

# In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

Convection

Conduction

Both convection and conduction

What is the correct answer?

4

# According of Kirchhoff's law

Radiant heat is proportional to fourth power of absolute temperature

Emissive power depends on temperature

Emissive power and absorptivity are constant for all bodies

Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body.

What is the correct answer?

4

# The value of the wavelength for maximum emissive power is given by

Wien's law

Planck's law

Stefan's law

Fourier's law

What is the correct answer?

4

# 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

What is the correct answer?

4

# According to Wien's law, the wavelength corresponding to maximum energy is proportion to

Absolute temperature (T)

F

T

What is the correct answer?

4

# The value of the wave length for maximum emissive power is given by

Kirchhoff's law

Stefan's law

Wines law

Planck's law

What is the correct answer?

4

# 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

What is the correct answer?

4

# Heat transfer takes place as per

Zeroth law of thermodynamics

First law of thermodynamic

Second law of the thermodynamics

Kirchoff's law

What is the correct answer?

4

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

Same

More

Less

Depends on other factors

What is the correct answer?

4

# Cork is a good insulator because it has

Free electrons

Atoms colliding frequency

Low density

Porous body

What is the correct answer?

4

# Depending on the radiating properties, body will be transparent when

P = 0, x = 0 and a = 1

P=1, x = 0, and a = 0

P = 0, T= 1, and a = 0

X = 0, a + p = 1

What is the correct answer?

4

# 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

What is the correct answer?

4

# Temperature of steam at around 540°C can be measured by

Thermometer

Thermistor

Thermocouple

None of these

What is the correct answer?

4

# The concept of overall coefficient of heat transfer is used in case of heat transfer by

Conduction

Convection

Conduction and convection

What is the correct answer?

4

# Heat is closely related with

Liquids

Energy

Temperature

Entropy

What is the correct answer?

4

# Free convection flow depends on

Density

Coefficient of viscosity

Gravitational force

All of these