An ice box made of Styrofoam (Thermal conductivity =0.01 Jm-1s-1K-1) is used to keep liquids cool. It has a total wall area including lid of 0.8 text 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 J-s-1 ):

Question

An ice box made of Styrofoam (Thermal conductivity =0.01 Jm-1s-1K-1) is used to keep liquids cool. It has a total wall area including lid of 0.8 text 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 J-s-1 ): (A) 16 (B) 14 (C) 12 (D) 10

Tardigrade Admin · Accepted Answer

H=(Q/t)=(KA(θ 1-θ 2)/d) =(0.01× 0.8(30° -0° )/2× 10-2) =12 J-s-1

16

14

12

10

8

H=tQ​=dKA(θ1​−θ2​)​ =2×10−20.01×0.8(30∘−0∘)​ =12J−s−1

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