HARD

Earn 100

A composite block is made of slabs A,B,C,D and E of different thermal conductivities ( given in terms of a constant K ) and size ( given in terms of length, L) as shown in the figure. All slabs are of same width. Heat Q flows only from left to right through the blocks. Then in steady state

12.5% studentsanswered this correctly

Important Questions on Thermal Properties of Matter

HARD

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

A thin piece of thermal conductor of constant thermal conductivity insulated on the lateral sides connects two reservoirs which are maintained at temperatures, $T_{1}$ and, $T_{2}$ as shown. Assuming that the system is in steady-state, which of the following plots best represents the dependence of the rate of change of entropy on the ratio of temperatures, $\frac{T_{1}}{T_{2}}$

Question Image

MEDIUM

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

Six identical conducting rods are joined as shown in the figure. Points

A

and

D

are maintained at

200^{o} C

and

20^{o} C

, respectively. The temperature of junction

B

will be

EASY

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

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:

MEDIUM

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

A metallic prong consists of $4$ rods made of the same material, cross-section, and same lengths as shown.

Question Image

The three forked ends are kept at $100^{o} C$ and the handle end is at $0^{o} C .$ The temperature of the junction is

MEDIUM

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

Two heater coils separately take

10 \min

and

5 \min

to boil a certain amount of water. If both the coils are connected in series, the time taken to boil water is

HARD

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

Two rectangular blocks, having identical dimensions, can be arranged either in configuration

I

or in configuration

I I

as shown in the figure. One of the blocks has thermal conductivity

K

and the other

2 K

. The temperature difference between the ends along the x-axis is the same in both the configurations. It takes

9 s

to transport a certain amount of heat from the hot end to cold end in the configuration

I

. The time to transport the same amount of heat in the configuration

II

MEDIUM

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

A cylinder of radius

R

is surrounded by a cylindrical shell of inner radius

R

and outer radius

2 R

. The thermal conductivity of the material of the inner cylinder is

K_{1}

and that of the outer cylinder is

K_{2}

. Assuming no loss of heat, the effective thermal conductivity of the system for heat flowing along the length of the cylinder is:

MEDIUM

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

Three rods of identical cross-section and length are made of three different materials of thermal conductivity $K_{1}, K_{2}$ and $K_{3}$ , respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at $100 ° C$ and the other at $0 ° C$ (see figure). If the joints of the rod are at $70 ° C$ and $20 ° C$ in steady and there is no loss of energy from the surface of the rod, the correct relationship between $K_{1}, K_{2}$ and $K_{3}$ is :

Question Image

EASY

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

A thick walled, hollow metallic cylinder has height

h

and inner and outer radii

r_{1}

and

r_{2}

, respectively. It contains water which is heated with a constant power source so that its temperature is maintained at

T_{1}

. In the steady state, the temperature of the inner and outer isothermal surfaces of the cylinder are

T_{1}

and

T_{2}

, respectively. The temperature difference

(T_{1} - T_{2})

is proportional to

MEDIUM

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

An iron slab and a copper slab having rectangular cross-sections and identical dimensions are welded together end to end. The outer ends of iron and copper slabs are held at

0 ° C

and

100 ° C

respectively. The thermal conductivities of iron and copper are

80 W \cdot m^{- 1} \cdot K^{- 1}

and

400 W \cdot m^{- 1} \cdot K^{- 1}

, respectively. Then, ignoring convective anc radiative losses, the temperature of the junction is close to

EASY

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

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

Question Image

HARD

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

Three rods of Copper, Brass and Steel are welded together to form a Y-shaped structure. Area of cross-section of each rod is

4 {cm}^{2}

. End of copper rod is maintained at

100 ° C

. Where as ends of brass and steel are kept at

0 ° C

. Lengths of the copper, brass and steel rods are

46, 13

and

12 cms

respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are

0.92, 0.26

and

0.12

CGS units respectively. Rate of heat flow through copper rod is :

EASY

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

The unit of thermal conductivity is

EASY

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

The two ends of a metal rod are maintained at temperatures

100 ° C

and

110 ° C

. The rate of heat flow in the rod is found to be

4.0 J s^{- 1}

. If the ends are maintained at temperatures

200 ° C

and

210 ° C

, the rate of heat flow will be:

MEDIUM

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

Two materials having coefficients of thermal conductivity

3 K

and

K

and thickness

d

and

3 d

respectively, are joined to form a slab as shown in the figure. The temperatures of the outer surfaces are

θ_{2}

and

θ_{1}

respectively,

(θ_{2} > θ_{1})

. The temperature at the interface is
Question Image

EASY

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

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

HARD

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

Consider a pair of insulating blocks with thermal resistances $R_{1}$ , and $R_{2}$ as shown in the figure. The temperature $θ$ at the boundary between the two blocks is

Question Image

MEDIUM

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

Two metallic wires of identical dimensions are connected is series. If

σ_{1}

and

σ_{2}

are the conductivities of the these wires respectively, the effective conductivity of the combination is :

EASY

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

The temperature $θ$ at the junction of two insulating sheets, having thermal resistances $R_{1}$ and $R_{2}$ as well as top and bottom temperatures $θ_{1}$ and $θ_{2}$ (as shown in figure) is given by :

Question Image

MEDIUM

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

Two conducting cylinders of equal length but different radii are connected in series between two heat baths kept at temperatures

T_{1} = 300 K a n d T_{2} = 100 K

as shown in the figure. The radius of the bigger cylinder is twice that of the smaller one and the thermal conductivities of the materials of the smaller and the larger cylinders are

K_{1} a n d K_{2}

, respectively. If the temperature at the junction of the two cylinders in the steady state is

200 K

, then

K_{1} / K_{2}

A composite block is made of slabs A,B,C,D and E of different thermal conductivities ( given in terms of a constant K ) and size ( given in terms of length, L) as shown in the figure. All slabs are of same width. Heat Q flows only from left to right through the blocks. Then in steady state

Important Questions on Thermal Properties of Matter

Learn and Prepare for any exam you want !