A metal rod of length 2m has cross sectional areas 2A and A as shown in figure. The ends are maintained at temperatures 100°C and 70°C. The temperature at middle point C is

Three rods of the same dimension have thermal conductivities $3K,2K$ and $K$. They are arranged as shown in figure given below, with their ends at $100°\mathrm{C},50°\mathrm{C}$ and $20°\mathrm{C}$. The temperature of their junction is

Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities $K_1, K_2$ and $K_3$. The points $P$ and $Q$ are maintained at different temperatures. For the heat flow at the same rate along $PRQ$ and $PQ$ which of the following option is correct?

A composite metallic bar of uniform cross-section is made up of length $25 \mathrm{cm}$ of copper, $10 \mathrm{cm}$ of nickel and $15 \mathrm{cm}$ of aluminium, each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at $100°\mathrm{C}$ and the aluminium end at $0°\mathrm{C}$. The whole rod is covered with belt so that there is no heat loss at the sides. If $K_{\mathrm{Cu}}=2K_{\mathrm{Al}}$ and $K_{\mathrm{Al}}=3K_{\mathrm{Ni}}$, then what will be the temperatures of $\mathrm{Cu}-\mathrm{Ni}$ and $\mathrm{Ni}-\mathrm{Al}$ junctions, respectively?