Thermal Energy and Heat Transfer

IMPORTANT

Thermal Energy and Heat Transfer: Overview

This Topic covers sub-topics such as Heat, Wien's Displacement Law, Thermal Convection and, Transfer of Heat by Convection in Air

Important Questions on Thermal Energy and Heat Transfer

EASY
IMPORTANT

The wavelength of maximum intensity for emitted radiation from a source is 11×105 cm.  The temperature of this source is n times the temperature of some other source for which the wavelength at maximum intensity is known to be 5.5×105 cm. Find the value of n.

EASY
IMPORTANT

A black body is at temperature 2880 K. The energy of radiation emitted by the body at wavelength 250 nm is U1, at wavelength 500 nm is U2 and that of 1000 nm is U3. Then the correct answer is (Weins constant b=2.88×106 nmK

EASY
IMPORTANT

The climate of the place is affected by its distance from the sea.

EASY
IMPORTANT

Explain how liquids and gases are heated?

EASY
IMPORTANT

Choose the correct word from the following options:

Land and sea breezes are caused due to:-

HARD
IMPORTANT

The formula λmT = 0.29 cm K  is used to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. Find the value of temperature(in K) for λm=5×10-5 cm.

MEDIUM
IMPORTANT

A black body emits radiations of maximum intensity at 5000 A when its temperature is 1227°C. If, its temperature is increased by 1000°C  then the maximum intensity of emitted radiation will be at:

MEDIUM
IMPORTANT

The wavelength of maximum intensity of radiation emitted by a star is 289.8 nm. The radiation intensity of the star is
(Stefan's constant =5.67×10-8 W m-2 K-4, Wien's constant =b=2898 μm K

MEDIUM
IMPORTANT

Experimental investigation shows that the intensity of solar radiation is maximum for a wavelength 480 nm in the visible region. Estimate the surface temperature of sun. (Given Wien's constant b=2.88×10-3 m K)

EASY
IMPORTANT

Generally the temperature of a distant star is estimated using

EASY
IMPORTANT

The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by

MEDIUM
IMPORTANT

The black body spectrum of an object Q1 is such that its radiant intensity (i.e., intensity per unit wavelength interval) is maximum at a wavelength of 100 nm. Another object O2 has the maximum radiant intensity at 600 nm. The ratio of power emitted per unit area by source O1 to that of source O2 is

EASY
IMPORTANT

According to Wien's law

EASY
IMPORTANT

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U1 , at wavelength 500 nm is U2 and that at 1000 nm is U3 . Wien's constant, b=2.88×106 nmK. Which of the following is correct?

EASY
IMPORTANT

Following graphs show the variation in the intensity of heat radiations by the black body and frequency at a fixed temperature. Choose the correct option.

MEDIUM
IMPORTANT

The spectral energy distribution of the Sun (temperature=6050 K) has a maximum at 4753 Å. The temperature of a star for which this maximum is at 9506 Å is

EASY
IMPORTANT

Following graph shows the correct variation in intensity of heat radiations by black body and frequency at a fixed temperature

MEDIUM
IMPORTANT

Following graph shows the correct variation in intensity of heat radiations by black body and frequency at a fixed temperature

EASY
IMPORTANT

On observing light from three different stars P,Q and R, it was found that intensity of violet colour is maximum in the spectrum of P, the intensity of green colour is maximum in the spectrum of R and the intensity of red colour is maximum in the spectrum of Q. If Tp, TQ and TR are the respective absolute temperatures of P, Q and R, then it can be concluded from the above observations that :

MEDIUM
IMPORTANT

Assertion: The temperature of a red-hot body is lower than that of a white-hot body.

Reason: This follows from Wien's displacement law : λm . T = constant .