Question

The area of the glass of a window of a room is $10m^2$ and thickness 2mm. The outer and inner temperature are ${40}^{\circ }$ C and ${20}^{\circ }$ C respectively. Thermal conductivity of glass in MKS system is 0.2. The heat flowing in the room per second will be

• A. $3\times {10}^{4}joules$
  
• B. $2\times {10}^{4}joules$
• C. 30 joules
• D. 45 joules

Answer 1

The correct option is B $2\times {10}^{4}joules$

$\frac{Q}{t}=\frac{KA({\theta }_1-{\theta }_2)}{l}=\frac{0.2\times 10\times 20}{2\times {10}^{-3}}=2\times {10}^{4}J/sec$