A $5cm$ thick ice block is there on the surface of water in a lake. The temperature of air is $-10°C$ ; how much time it will take to double the thickness of the block ...... hour ($L = 80 cal/g, Kicc = 0.004 Erg/s-k, dice = 0.92 g cm^{-3}$)
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Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities $K1, K2, K3, K4$ and $K5$ . When points $A$ and $B$ are maintained at different temperatures, no heat flows through the central rod if
Three identical rods $AB$, $CD$ and $PQ$ are joined as shown. $P$ and $Q$ are mid points of $AB$ and $CD$ respectively. Ends $A, B, C$ and $D$ are maintained at $0^o C, 100^o C, 30^o C$ and $60^o C$ respectively. The direction of heat flow in $PQ$ is
The plots of intensity versus wavelength for three black bodies at temperatures $T_1, T_2$ and $T_3$ respectively are as shown. Their temperature are such that
For a black body at temperature $727^{\circ} C$, its radiating power is $60\; watt$ and temperature of surrounding is $227^{\circ} C$. If temperature of black body is changed to $1227^{\circ} C$ then its radiating power will be ..... $watt$
In the Arctic region, hemispherical houses called Igloos are made of ice. It is possible to maintain a temperature inside an Igloo as high as $20^{\circ} C$ because
Hot water kept in a beaker placed in a room cools from ${70^o}C$ to $60°C$ in $4$ minutes. The time taken by it to cool from ${69^o}C$ to ${59^o}c$ will be
The ends of two rods of different materials with their thermal conductivities, radii of cross-sections and lengths all are in the ratio $1:2$ are maintained at the same temperature difference. If the rate of flow of heat in the larger rod is $4\;cal/\sec $, that in the shorter rod in $cal/\sec $ will be
A body cools from ${60^o}C$ to ${50^o}C$ in $10$ minutes. If the room temperature is ${25^o}C$ and assuming Newton's law of cooling to hold good, the temperature of the body at the end of the next $10$ minutes will be ......... $^oC$