Heat current is maximum in which of the following (rods are of identical dimension) ?

One kilogram of ice at $0°$C is mixed with one kilogram of water at 80$°C$. The final temperature of the mixture is (Take: Specific heat of water = 4200 J $k{g}^{-1}{C}^{-1}$, Latent heat of ice = 336 kJ $k{g}^{-1}$)

The fastest mode of heat transfer is 

A temperature of 100 ^oF (Fahrenheit scale) is equal to T K (Kelvin scale). The value of T is:

A black body at temperature 300K radiates heat at the rate E. If its temperature is increased by 600K, the rate of radiation will increase to -

A body cools down from $80°\mathrm{C} \mathrm{to} 70°\mathrm{C}$ in 5 minutes. The temperature of the same body will fall from $70°\mathrm{C} \mathrm{to} 60°\mathrm{C}$ in:

If ${\lambda }_m$ is the wavelength, corresponding to which the radiant intensity of a block is at its maximum and its absolute temperature is T, then which of the following graph correctly represents the variation of T.

Heat capacity is equal to the product of:

When a block of iron floats in Hg at $0°C$, a fraction $K_1$ of its volumen= is submerged, while at temperature of $60°C$ a fraction $K_2$ is seen to be submersed. If the coefficient of volume expansion of iron is ${\gamma }_{Fe}$ and that of mercury is ${\gamma }_{Hg}$, then the ratio $\frac{K_1}{K_2}$ can be expressed as:

Hot water cools from 60$°\mathrm{C}$ to 50$°\mathrm{C}$ in first 10 minutes and from 50$°\mathrm{C}$ to 42$°\mathrm{C}$ in next 10 minutes. The temperature of surrounding is :

A pendulum clock runs faster by 5 seconds per day at 20 ^oC and goes slow by 10 second per day at 35 ^oC. It shows the correct time at a temperature of:

A constrained steel rod of length l, area of cross-section A, Young's modulus Y and coefficient of linear expansion $\alpha$ is heated through $t°C$. The work that can be performed by the rod when heated is:

The temperature of a body on Kelvin scale is found to be X K. When it is measured by a Fahrenheit thermometer, it is found to be X⁰F. Then X is

Two rods, A and B, of different materials having the same cross-sectional area are welded together as shown in the figure. Their thermal conductivities are $K_1$ and $K_2$. The thermal conductivity of the composite rod will be:

A spherical black body with a radius of 12 cm radiates 450-watt power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watts would be:

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at ${100}^{°}$ C, while the other one is at $0^{° }$C. If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is -

A body cools from a temperature 3T to 2T in10 minutes. The room temperature is T. Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next 10 minutes will be -

(a) $\frac{7}{4}T$    (b) $\frac{3}{2}T$

(c) $\frac{4}{3}T$    (d) $T$

The coefficients of linear expansion of brass and steel rods are α₁ and α₂, lengths of brass and steel rods are l₁ and l₂ respectively. If (l₂ - l₁) is maintained the same at all temperatures, Which one of the following relations holds good?

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at a wavelength of 250 nm is U₁, at a wavelength of 500nm is U₂ and that at 1000nm is U₃. Given Wien's constant $b=2.88\times {10}^6 nm-\mathrm{K,\; which }$of the following is correct?
 

Two metal wires of identical dimensions are connected in series. If $\sigma$₁ and $\sigma$₂ are the conductivities of the metal wires respectively, the effective conductivity of the combination is

The value of coefficient of volume expansion of glycerin is 5x10^-4 K^-1. The fractional change in the density of glycerin for a rise of 40°C in its temperature is -

Steam at 100°C is passed into 20 g of water at 10°C. When water acquires a temperature of 80°C, the mass of water present will be (Take specific heat of water=1 cal g^-1 °C^-1 and latent heat of steam = 540 cal g^-1)

A certain quantity of water cools from 70°C to 60°C in the first 5 minutes and to 54°C in the next 5 minutes. 
The temperature of the surroundings will be: 

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

Liquid oxygen at 50K is heated to 300K at constant pressure of 1 atm. The rate of heating is constant.Which one of the following graphs represents the variation of temperature with time?

In one hour 4.8 kg of ice is melted. The thermal

thickness 0.1 m is exposed on the lower 

A slab of stone of area of 0.36 ${\mathrm{m}}^2$ and 

surface to steam at $100°\mathrm{C}$. A block of ice 

at $0°\mathrm{C}$ rests on the upper surface of the slab.

conductivity of slab is

(Given latent heat of fusion of ice 

=3.36x${10}^{5 }\mathrm{J} {\mathrm{kg}}^{-1}$)

(a) $1.24 \mathrm{J}/\mathrm{m}/\mathrm{s}/°\mathrm{C}$        (b) $1.29 \mathrm{J}/\mathrm{m}/\mathrm{s}/°\mathrm{C}$

(c) $2.05 \mathrm{J}/\mathrm{m}/\mathrm{s}/°\mathrm{C}$        (d) $1.02 \mathrm{J}/\mathrm{m}/\mathrm{s}/°\mathrm{C}$

On a clear sunny day, an object at temperature T is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of the mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object placed on the top of a mountain will register a temperature:

Heat travels through vacuum by 

When 1 kg of ice at $0°\mathrm{C}$ melts to water at $0°\mathrm{C}$, the resulting change in its entropy, taking latent heat of ice to be $80 \mathrm{cal}/\mathrm{g},$ is

A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reserviors in time t ?