Thermal Propert...

An ideal black body at room temperature is thrown into a furnance. It is observed that

Three objects coloured black, grey and white can with stand hostile conditions at 2800°C. These objects are thrown into furnace where each of them attains a temperature of 2000°C. Which object will glow brightest?

A perfect black body is one whose emissive power is

2 L of water at initial temperature of 27°C is heated by a heater of power 1 kW. If the lid of kettle is opened, then heat is lost at the constant rate of 160 J/s. Find the time required to raise the temperature of water to 77°C with the lid open (specific heat of water 4.2 kJ/kg).

Same quantity of ice is filled in each of the two metal containers P and Q having the same size, shape and wall thickness but made of different materials. The containers are kept in identical surroundings. The ice in P melts completely in time t₁ whereas in Q takes a time t₂. The ratio of thermal conductivities of the materials of P and Q is

A very small hole in an electric furnace is used for heating metals. The hole nearly acts as a black body. The area of the hole is 200 mm². To keep a metal at 727°C, heat energy flowing through this hole per sec, in joules is (σ = 5.67 × 10^-8Wm^-2K^-4 )

A cane is taken out from a refrigerator at 0°C. The atmospheric temperature is 25°C. If t1 is the time taken to heat from 0°C to 5°C and t2 is the time taken from 10°C to 15°C, then

A body cools down from 65°C to 60°C in 5 min. It will cool down from 60°C to 55°C in

Hot food cools from 94°C to 86°C in 2 min when the room temperature is 20°C. How long would the food take to cool from 71°C to 69°C?

The quantities of heat required to raise the temperatures of two copper spheres of radii r₁ and r₂ (r₁ =1.5 r₂ ) through 1 K are in the ratio of