Two identical rods of a metal are welded in series. Then 20 cal of heat flows through them in 4 minutes. If the rods are welded in parallel, then the same amount of heat will flow in N minutes. Find N.
Physics · Mixed Chapter
JEE Main Practice

Question

Two identical rods of a metal are welded in series. Then 20 cal of heat flows through them in 4 minutes. If the rods are welded in parallel, then the same amount of heat will flow in N minutes. Find N.

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1: Let the thermal resistance of each identical rod be R. Step 2: In series, Rₛ = R + R = 2R. In parallel, Rₚ = R/2. Step 3: With the same temperature difference, heat current is inversely proportional to thermal resistance: Hₚ/Hₛ = Rₛ/Rₚ = 4. Step 4: For the same heat quantity, time is inversely proportional to heat current: tₚ = 4/4 = 1 min. Final answer: N = 1.