An ice box made of Styrofoam (thermal conductivity =0.01Jm=1K) is used to keep liquids cool. It has a total wall area including lid of0.8 m2 and wall thickness of 2.0 cm. A bottle of water is placed in the box and filled with ice. If the outside temperature is 30?C, the rate of flow of, heat into the box is (in Js-1)

Question

An ice box made of Styrofoam (thermal conductivity =0.01Jm=1K) is used to keep liquids cool. It has a total wall area including lid of0.8 m2 and wall thickness of 2.0 cm. A bottle of water is placed in the box and filled with ice. If the outside temperature is 30?C, the rate of flow of, heat into the box is (in Js-1) (A) 16 (B) 14 (C) 12 (D) 10

Tardigrade Admin · Accepted Answer

H=(Q/t)=(KA(θ 1-θ 2)/l)=(0.01× 0.8(30-0)/2× 10-2) =12 JS-1

16

14

12

10

H=tQ​=lKA(θ1​−θ2​)​=2×10−20.01×0.8(30−0)​ =12JS−1

$H = \frac{Q}{t} = \frac{K A ( θ _{1} - θ _{2} )}{l} = \frac{0.01 \times 0.8 ( 30 - 0 )}{2 \times 10 ^{- 2}}$ $= 12 J S^{- 1}$