Question

A cylindrical rod having temperature `T_(1)` and `T_(2)` at its ends. The rate of flow of heat is `Q_(1) cal//sec`. If all the linear dimensions are doubled keeping temperature constant, then rate of flow of heat `Q_(2)` will be
A. `4 Q_(1)`
B. `2Q_(1)`
C. `(Q_(1))/4`
D. `(Q_(1))/2`

Answer 1

Correct Answer - B
`Q_(1)=(DeltaT)/((l/(k pir^(2)))), Q_(2)=(DeltaT)/((2l)/(kpi(2r)^(2)))rArr (Q_(2))/(Q_(1))=2`