A sphere, a cube and a thin circular plate, all made of same material and having the same mass are initially heated to the same temperature of 200° C, which of them cools fastest when left in air at room temperature:

Question

A sphere, a cube and a thin circular plate, all made of same material and having the same mass are initially heated to the same temperature of 200° C, which of them cools fastest when left in air at room temperature: (A) sphere (B) cube (C) circular plate (D) all at the same rate

Tardigrade Admin · Accepted Answer

Rate of flow of heat is given by H=(K A Δ θ/l) where A is area, K the coefficient of thermal conduction, A 6 the change in temperature. ∴ H propto Area (A) Since, surface area is maximum for circular plate, hence it cools fastest.

Q. A sphere, a cube and a thin circular plate, all made of same material and having the same mass are initially heated to the same temperature of $20 0^{\circ} C$ , which of them cools fastest when left in air at room temperature:

sphere

cube

circular plate

all at the same rate

Rate of flow of heat is given by $H = \frac{K A Δ θ}{l}$
where $A$ is area, $K$ the coefficient of thermal conduction,
$A 6$ the change in temperature.
$∴ H \propto$ Area $(A)$
Since, surface area is maximum for circular plate, hence it cools fastest.

Q. A sphere, a cube and a thin circular plate, all made of same material and having the same mass are initially heated to the same temperature of 200∘C, which of them cools fastest when left in air at room temperature: