Two thin blankets keep more hotness than one blanket of thickness equal to these two. The reason is
A
Their surface area increases
B
A layer of air is formed between these two blankets, which is bad conductor
C
These have more wool
D
They absorb more heat from outside
Easy
Download our app for free and get started
B
A layer of air is formed between these two blankets, which is bad conductor
b (b) Two thin blankets usually warmer than one thick blanket because air is trapped between them. And the air is bad conductor of heat. It does not pass heat from our body to the surroundings.
Download our app
and get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Two rods (one semi-circular and other straight) of same material and of same cross-sectional area are joined as shown in the figure. The points $A$ and $B$ are maintained at different temperature. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a cross section of the straight rod in a given time is
Two plates $A$ and $B$ have thermal conductivities $84\,Wm ^{-1}\,K ^{-1}$ and $126\,Wm ^{-1}\,K ^{-1}$ respectively. They have same surface area and same thickness. They are placed in contact along their surfaces. If the temperatures of the outer surfaces of $A$ and $B$ are kept at $100^{\circ}\,C$ and $0{ }^{\circ}\,C$ respectively, then the temperature of the surface of contact in steady state is $..........\,{ }^{\circ} C$.
The total radiant energy per unit area, normal to the direction of incidence, received at a distance $R$ from the centre of a star of radius $r$, whose outer surface radiates as a black body at a temperature $T\ K$ is given by
A particular star (assuming it as a black body) has a surface temperature of about $5 \times {10^4}K.$The wavelength in nanometers at which its radiation becomes maximum is $(b = 0.0029 mK)$
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 reservoirs in time $t$ ?
A black body calorimeter filled with hot water cools from $60^o C$ to $50^o C$ in $4 \,\,min$ and $40^o C$ to $30^o C$ in $8 \,\min$. The approximate temperature of surrounding is ........ $^oC$
The coefficients of thermal conductivity of copper, mercury and glass are respectively $Kc, Km$ and $Kg$ such that $Kc > Km > Kg$ . If the same quantity of heat is to flow per second per unit area of each and corresponding temperature gradients are $Xc, Xm$ and $Xg$ , then