Question

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 $0°C$ , $100°C$ , $30°C$ and $60°C$ respectively. The direction of heat flow in $PQ$ is

• A. From $P$ to $Q$
• B. From $Q$ to $P$
• C. Heat does not flow in $PQ$
• D. Data not sufficient

Answer 1

Answer: (A)

assume that there is no ' $PQ$ ' Rod
Then ${\text{T}}_{\text{P}}=\frac{100}{2}=50{}^{{}^{\circ }}\text{C}$
${\text{T}}_{\text{Q}}=45{}^{{}^{\circ }}\text{C}$
${\text{T}}_{\text{P}}>{\text{T}}_{\text{Q}}\Rightarrow$ Heat flow from $P$ to $Q$