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The convection current which arises when equatorial and polar regions of the earth receive unequal solar heat is called as:

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Important Questions on Thermal Properties of Matter

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Statement $A :$ Convection involves flow of matter within a fluid due to unequal temperatures of its parts.

Statement $B :$ A hot bar placed under a running tap water loses heat due to effect of convection within water.

Statement. $C :$ Heat transfer always involves temperature difference between two systems.

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

If temperature of a black body increases from

300 K

900 K

, then the rate of energy radiation increases by

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Ordinary bodies

A

and

B

radiate maximum energy with wavelength difference

4 μ m

. The absolute temperature of body

A

3

times that of

B

. The wavelength at which body

B

radiates maximum energy is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

If temperature of black body increases from

17 ° C

307 ° C,

then the rate of radiation increases by

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

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

T_{p}, T_{Q}

and

T_{R}

are the respective absolute temperatures of

P

Q

and

R

, then it can be concluded from the above observations that :

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Prevost's theory of heat exchange is not applicable at temperature

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Three rods of identical cross-sectional area and made from the same metal, form the sides of an isosceles triangle

A B C

right angled at

B

as shown in figure. The point

A

and

B

are maintained at temperature

T

and

\sqrt{2} T

respectively, in the steady state. Now, assuming that only heat conduction takes place. The temperature of point

C

will be

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

A block of ice at,

0 ° C

is kept on the upper surface of a slab of thickness,

10 cm

and having a lower surface area of,

3360 {cm}^{2} .

The lower surface of the slab is exposed to steam at

100 ° C

5 g

of ice melts in

10 \min .

What is the thermal conductivity of the slab.

[

latent heat of fusion of ice

= 3.36 \times 10^{5} J {kg}^{- 1}]

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Two spherical black bodies have radii

r_{1}

and

r_{2}

. Their surface temperatures are

T_{1}

and

T_{2}

. If they radiate same power then

\frac{r_{2}}{r_{1}}

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are $K_{1}$ and $K_{2}$ . The thermal conductivity of the composite rod will be

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

Two identical metal wires of thermal conductivities

K_{1}

and

K_{2}

respectively are connected in series. The effective thermal conductivity of the combination is:

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

A heat source at

T = 10^{3} K

is connected to another heat reservoir at

T = 10^{2} K

by a copper slab which is

1 m

thick. Given that the thermal conductivity of copper is

0 .1 W K^{- 1} m^{- 1}

, the energy flux through it in the steady-state is:

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Convection

The plots of intensity versus wavelength for three black bodies at temperature $T_{1}$ , $T_{2}$ , $T_{3}$ , respectively, are shown in the figure. Their temperatures are such that

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