Thermal Conduction and Heat Transfer
Quiz covering thermal conduction, heat transfer, and thermal properties of metals and non-metals
Questions
For cooking the food, which of the following type of utensil is most suitable
- High specific heat and low conductivity
- High specific heat and high conductivity
- Low specific heat and low conductivity
- Low specific heat and high conductivity
Two walls of thickness $d _1$ and $d _2$, thermal conductivities $K _1$ and $K _2$ are in contact. In the steady state if the temperature at the outer surfaces are $T _1$ and $T _2$, the temperature are the common wall will be
- $\dfrac{K _1T _1+K _2T _2}{d _1d _2}$
- $\dfrac{K _1T _1d _2+K _2T _2d _1}{K _1d _2+K _2d _1}$
- $\dfrac{K _1d _1T _1+K _2d _2T _2}{K _1d _1+K _2d _2}$
- $\dfrac{(K _1d _1+K _2d _2)T _1T _2}{T _1+T _2}$
The area of cross - section of rod is given by $ A = a _0 (1 + \alpha x ) $ where $ A _{ 0 }\quad & \quad \alpha $ are constant and x is the distance from one end If thermal conductivity of material is K. What is the thermal resistance of the rod if its length is
- $ KA _{ 0 }\alpha \quad to\quad (1+a\ell _{ 0 }) $
- $ \frac { 1 }{ Ka _{ 0 }\alpha } \quad \ell n \quad (1+\alpha\ell _{ 0 })$
- $ \frac { \alpha }{ KA _{ 0 } } \quad \ell n\quad (1+a\ell _{ 0 }) $
- $ \frac { KA _{ 0 } }{ \alpha } \ell n(1+\alpha \ell _{ 0 })$
a container that suits the occurrence of an isothermal process should be made of
- Copper
- Glass
- Wood
- Cloth
The temperature of skin is $T _{skin} = 34^0C$ (somewhat less than the body temperature, $T _{body} = 37^0C$) and the ambient tempreature is $T _{room} = 24^0C$. The surface area of an adult is A $\simeq$ 1.85 $m^2$. Calculate the net heat loss of the person.
- 25 W
- 100 W
- 300 W
- 500 W
Consider a compound slab consisting of two different materials having equal thickness and thermals conductivities K and $2K$ in series. The equilvalent conductivity of the slab is
- $\frac{2}{3}K$
- $\sqrt {2K} $
- $3K$
- $\left( {\frac{4}{3}} \right)K$
Pick the odd one out. Give scientifc reason for your answer:
- Conduction, convection, fusion, radiation.
- Iron, aluminimum, asbestos, copper
- Felt, paper, silver, wood
- Ventilation, land breeze, sea breeze, thermos flask
A solid sphere and a hollow sphere of same material and size are heated to some temperature and allowed to cool in the same surroundings.If the temperature difference between each sphere and its surrounding is T, then:-
- The hollow sphere will cool at a faster rate for all values of T
- The solid sphere will cool at a faster rate for all values of T
- Both spheres will coll at the same rate for all values of T
- Both spheres will coll at the same rate only for small values of T
Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at ${ 100 }^{ 0 }$, while the other one is at ${ 0 }^{ 0 }C$. If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is
- ${ 50 }^{ 0 }C$
- more than ${ 50 }^{ 0 }C$
- less than ${ 50 }^{ 0 }C$ but greater than ${ 0 }^{ 0 }C$
- ${ 0 }^{ 0 }C$
In winter , temprature of bottom of take is 4$$C . Ratio of thermal conductance of ice and water is 2:3 and depth of the take 20 m. Find the maximum thickness os ice formed .
- $\frac { 200 }{ 11 } M$
- $\frac { 100 }{ 8 } M$
- $\frac { 220 }{ 12 } M$
- 10 M
A semicircular rod is joined at its end to a straight rod of the same material and the same cross-sectional area. The straight rod forms a diameter of the other rod. The junctions are maintained at different temperatures. Find the ratio of the heat transferred through a cross-section of the semicircular rod of the heat transferred through a cross-section the straight rod in the given time.
- $\dfrac 2\pi$
- $\dfrac 1\pi$
- $\dfrac 1{2\pi}$
- $\dfrac \pi2$
Bimetallic thermostat consists two metals of different thermal co-efficient thermostat always bends towards material having
(i)large thermal expansion on heating
(ii)large thermal expansion on cooling
(iii)small thermal expansion on heating
(iv)small thermal expansion on cooling
- I only
- II only
- III and II only
- I and IV only
The ratio of radii of two spheres of same material is $1:4 .$ Then the ratio of their heat capacity will be
- $\dfrac { 1 } { 64 }$
- $\dfrac { 1 } { 32 }$
- $\dfrac { 1 } { 2 }$
- $\dfrac { 1 } { 4 }$
Which of the following material is most suitable for cooking utensil ?
- Low conductivity and low specific heat
- High conductivity and low specific heat
- Low conductivity and High specific heat
- High conductivity and High specific heat
Two angular blocks A and B different metal have same length and same area of cross-section . they are kept in such a way that their cross-sectional area touch each other. the temperature at one end of A is $ 100^0 $ C and that of B at the other end is $0^0 C $ C . if the ratio of their conductivity is 1:3 then under steady state, the temperature of the junction in contact will be:-
- $ 25^0 C $
- $ 50^0 C $
- $ 75^0 C $
- $ 100^0 C $
On heating one end of a rod, the temperature of the whole rod will be uniform when the :
- $k $ $ = 1$
- $k $ $ = 0$
- $k $ $ = 100$
- $k $ $ = \infty $
A slab consists of two parallel layers of two difference materials of same thickness and having thermal conductivities $K _1$ and $K _2$. The equivalent thermal conductivity K of the slab is-
- $K _1+K _2$
- $\frac{2K _1K _2}{K _1+K _2}$
- $\frac{K _1+K _2}{K _1K _2}$
- $K _1K _2$
Which of the following represent practical uses each of good conductors of heat?
- <span>Cooking vessels are coated with copper at the base so as to readily absorb heat energy and get the food cooked quickly, thus saving time and fuel</span>
- <span>Mercury is used as a thermometric liquid as it is a good conductor of heat</span>
- <span>Cooling coils of refrigerators and air-conditioners are made of copper as they easily conduct away the heat </span>
- None of the above
On a cold morning, a metal surface in touching is felt colder than a wooden surface, because the metal has:
- low thermal condutivity
- high thermal conductivity
- high specific heat
- low specific heat
On a cold morning, a metal surface will feel colder to touch than a wooden surface, because:
- metal has high specific heat
- metal has high thermal conductivity
- metal has low specific heat
- metal has low thermal conductivity
Statement-1
On a chilly day, the metallic cap of a pen feels much colder than the plastic body although both are at the same (room) temperature.
Statement-2
Metal has a higher coefficient of thermal conductivity than plastic.
- Statement-1 is true, Statement-2 is true and Statement-2 is the correct explanation for Statement- 1
- Statement-1 is true, Statement-2 is true but Statement-2 is not the correct explanation for Staement-1
- Statement-1 is true, Statement-2 is false.
- Statement-1 is false, Statement-2 is true.
Metals are good conductors of heat because.
- They contain large number of free electrons
- Their atoms are relatively apart.
- Their atoms collide frequently.
- They have reflecting surfaces.