Three rods of equal length and area with thermal conductivities 3, 4 and 5 units are connected in series. Find effective conductivity (nearest integer).
Physics · Mixed Chapter
JEE Main Practice

Question

Three rods of equal length and area with thermal conductivities 3, 4 and 5 units are connected in series. Find effective conductivity (nearest integer).

G1 Physics · Accepted Answer

Step 1: For equal lengths, equivalent thermal resistance satisfies 3L/(kₑ𝒇𝒇A)=(L/A)(1/3+1/4+1/5). Step 2: 1/3+1/4+1/5=(20+15+12)/60=47/60. Step 3: kₑ𝒇𝒇=3×60/47≈3.83. Nearest integer is 4.