Related InterviewSolutions

• Three objects coloured black, gray and white can withstand hostile conditions upto `2800^(@)C`. These objects are thrown into a furance where each of them attains a temperature of `2000^(@)C`. Which object will glow brightest?A. The white objectB. The black objectC. All glow with equal brightnessD. Grey object
• A black body maintained at a certain temperature radiates heat energy at the rate `Q` watt. If its surface is smoothened so as to lower its emissivitiy by 10%, what will be the increase in its rate of radiation at double the initial temperature?A. `(0.9xx102^(4)-1)Q` wattB. `0.9xx2^(4)Q` wattC. `(0.9xx2)^(4)Q` wattD. `(0.9)^(4)xx2Q` watt
• A uniform metal ring with centre `C` have two points `A` and `B` such that angle `ACB` is `theta`. `A` and `B` are maintained at two different constant temperature. If the angle between `A` and `B` i.e. `theta=180^(@)` the rate of heat flow from `A` and`B` is `1.2W`, then what will be the rate, when `theta=90^(@)`?A. `0.6W`B. `0.9W`C. `1.6W`D. `1.8W`
• What amount of ice at `-14^(@)C` required to cool `200gg` of water from `25^(@)C` to 10CC? (Given `C_("ice")=0.5cal/g.^(@)C,L_(f)` for ice `=80cal//g`)A. `31g`B. `41g`C. `51g`D. `21g`
• An aluminium rod of length `L` and cross-sectional area `2A` is joined with a copper rod of length `2L` and area of cross-section is `A` as shown in figure. Find the temperature of aluminium-copper junction in the steady state of the system. Given thermal conductivity `K_(Al)=240J//m//s//.^(@)C, K_(Cu)=400J//m//s//.^(@)C`A. `300^(@)C`B. `400^(@)C`C. `288.24^(@)C`D. `275.4^(@)C`
• Find the time in which a layer of ice thickness `h` will grow on the surface of the pond of surface area `A`, when the surrounding temperature falls to `-T^(@)C`. (Assume `K=` thermal conductivity of ice, `rho-` densityy of water `L=` latent heat of fusion)A. `t=(rhoL)/(2KT)h^(2)`B. `t-(rhoL)/(KT)h^(2)`C. `t=(rhoLh^(2))/(3KT)`D. `t=(rhoLh^(2))/(4KT)`
• A sphere a cube and a thin circular plate all of same material having same mass are initially heated to `200^(@)C`. Which of these will cool fastest?A. Circular plateB. SphereC. CubeD. All of these
• Two spheres of the same material having radii `r` and `4r` and temperature `2T_(0)` and `T_(0)` respectively. The ratio of rate of radiation of energy by the sphere isA. `1:1`B. `1:2`C. `2:1`D. `3:1`