Q. Four identical rods of same material are joined end to end to form a square. If the temperature difference between the ends of a diagonal is $100℃$, then the temperature difference between the ends of other diagonal will be
A) $0℃$
B) $\frac{100}{l}℃$; where $l$ is the length of each rod
C) $\frac{100}{2l}℃$
D) $100℃$
Explanation
(a) Suppose temperature difference between $A$ and $B$ is $100℃$ and $\theta_{A} > \theta_{B}$
Heat current will flow from $A$ and $B$ via path $ACB$ and $ADB$. Since all the rods are
identical so $(\mathrm{\Delta}\theta)_{AC} = (\mathrm{\Delta}\theta)_{AD}$
[Because heat current $H = \frac{\mathrm{\Delta}\theta}{R}$; here $R =$ same for all]
$\Rightarrow \theta_{A} - \theta_{C} = \theta_{A} - \theta_{D} \Rightarrow \theta_{C} - \theta_{D}$
$i.e.$ temperature difference between $C$ and $D$ will be zero
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.