Two rods of same length and material transfer a given amount of heat in $12\,s,$ when they are joined end to end. But when they are joined lengthwise, then they will transfer same heat in same conditions in .......... $\sec$
$24$
$3$
$1.5$
$48$
Two sheets of thickness $d$ and $2 d$ and same area are touching each other on their face. Temperature $T_A$, $T_B$, $T_C$ shown are in geometric progression with common ratio $r = 2$. Then ratio of thermal conductivity of thinner and thicker sheet are
Two large holes are cut in a metal sheet. If this is heated, distances $AB$ and $BC$, (as shown)
Two identical square rods of metal are welded end to end as shown in figure $(a),\, 20$ $calories$ of heat flows through it in $4\,minutes$ . If the rods are welded as shown in figure $(b)$ , the same amount of heat will flow through the rods in ...... $\min$
Solar radiation emitted by the sun resembles that emitted by a black body at a temperature of $6000\, K$. Maximum intensity is emitted at a wavelength of about $4800\,\mathop A\limits^o $. If the sun was cooled down from $6000\, K$ to $3000\, K$, then the peak intensity would occur at a wavelength of ......... $\mathop A\limits^o $
If the temperature of the sun were to increase from $T$ to $2T$ and its radius from $R$ to $2R$, then the ratio of the radiant energy received on earth to what it was previously will be