Question

Calculate the rate of loss of heat through a glass window of area $1000\, cm ^{2}$ and thickness $0.4 \,cm$ when temperature inside is $37^{0}$ and outside is $-5^{0}$. (K glass $\left.=2.2 \times 10^{-3}\, cals ^{-1} \,cm ^{-1} \,K ^{-1}\right)$

• A. 450 cal/s
• B. 231 cal/s
• C. 439 cal/s
• D. 650 cal/s

Answer 1

Answer: (B)

$\frac{Q}{t}=\frac{K A \Delta \theta}{L}$
$=\frac{2.2 \times 10^{-3} \times 10^{3} \times 42}{4 \times 10^{-1}}$
$=231 \,cal / s$