KCET 2025 Physics Paper

To determine the temperature at the junction x of three identical metal rods, follow this analysis:
Assuming No Heat Loss: The rods are made of the same material and are identical, ensuring consistent heat flow throughout.
Thermal Resistance: Let the thermal resistance of each rod be R. The temperature at the junction is Tx.
Heat Flow Equilibrium: Since the system reaches a steady state, the heat flowing into the junction from each side should equal the heat flowing out:
H=H1+H2
Where:
H is the heat flowing into the junction from both ends.
H1 and H2 are the heat flows from the sides of the junction.
Application: Set up the heat balance equation:
‌

Tx−0

R

=‌

90−Tx

R

+‌

90−Tx

R

Simplifying: Substitute and solve:
Tx=‌

180

3

=60∘C
Therefore, the temperature at the junction x is 60∘C. This calculation assumes perfect thermal conduction and no heat loss outside the system.