The walls of a closed cubical box of edge` 40 cm` are made of a material of thickness `1 mm` and thermal conductivity `4 xx 10^(-4) cals^(-1@) C^(-1)`. The interior of the box is maintained at `100 ^(@) C` above the outside temperature by a heater placed inside the box and connected across `400 V dc` . Calculate the resistance of the heater.

The walls of a closed cubical box of edge 50cm are mdade of a material of thickness 1mm and thermal conductivity 4xx10^(-4) cal s^(-1)cm^(-1).^(@)C^(-1) the interior of the box maintained at 100^(@)C above the outside temperature by a heater placed inside the box and connected acros a 400 V d.c. source. Calculate the resistance of the heater.

The walls of a closed cubical box of edge 50cm are made of a material of thickness 1mm and thermal conductivity 4xx10^(-4) cm^(-1)(.^@C)^(-1) . The interior of the box is maintained 100^(@)C above the outside temperature by a heater placed inside the box and connected across 420V d.c. calculate the resistance of copper.

A slab consists of two parallel layers of different materials 4cm and 2cm thick and of thermal conductivities 54cals^(-1)m^(-1)K^(-1) and 36cals^(-1)m^(-1)K^(-1) respectively. If the faces of the slab are at 100^(@)C and 0^(@)C calculate the temperature of the surface dividing the two materials.

Steam at 373K is passed through a tube of radius 50 cm and length 3m. If thickness of the tube be 2 mm and conductivity of its material be 2xx10^(-4) / cal/s-cm-K, the rate of loss of heat in Js^(-1) is (The outside temperature is 282K).

Steam at 100^(@)C is passed through a tubeof radius 5 cm and length 3 m. If the thickness of tube be 2 mm and conductivity of its material be 2xx10^(-4)" cal "cm^(-1) K^(-1) s^(-1) , calculate the rate of loss of heat in js^(-1) . The outside temperature is 20^(@)C .

Steam at 373 K is passed through a tube of radius 10 cm and length 10 cm and length 2m . The thickness of the tube is 5mm and thermal conductivity of the material is 390 W m^(-1) K^(-1) , calculate the heat lost per second. The outside temperature is 0^(@)C .

A cube of side 10cm is filled with ice of density 0.9//c.c Thickness of the walls of the cube is 1mm and thermal conductivity of the material of the cube is steam bath maintained at a placed in steam bath maintained at a temperature of 100^(@)C the time in which ice completely melts is (L_(ice)=80cal//gm) .

Water is filled in a closed cylindrical vessel of 10 cm height and base radius sqrt(10//pi) cm. The open ends ofthe cylinder are closed by two metal discs made ofa material whose thickness is 10^(-3)m and having thermal conductivity 200W//m^(@)C. If water temperature inside the cylinder is 50^(@)C and surrounding temperature is 20^(@)C, findthe time taken for the temperature to fall by 1^(@)C, Given that the specific heat ofwater is 4200J//kg^(@)C. and heat loss from water only takes place by the discs as the walls are made up of a thermally insulating material.

A 100 W heater is placed in a cubical container of edge length 6xx10^(-2)m. The wall thick ness of the container is 1 mm. If inside and outside temperature in steady state are 30^(@)C. and 25^(@)C, find the thermal conductivity of the material of the box.

A sperical shell , made of material of electrical conductivity 10^9//pi(Omegam)^(-1) , has thickness t = 2 mm and radius R = 10 cm. In an arrangement, its inside surface is kept at a lower potential than its outside surface. The resistance offered by the shell is equal to