Question

At what rate is heat lost through a 1.5 m × 2.5 m rectangular glass windowpane that is 0.4 cm thick when the inside temperature is 25 °C and the outside temperature is 5.0 °C? The thermal conductivity for the glass is 0.78 W/(m · C°).


Select one:
A. 14 600 W
B. 146 W
C. 702 W
D. 13 500 W
E. 7200 W

Answer 1

Answer:

It helps to you

So ,Answer is "D"

"D"=13,500W

Answer 2

Given : a 1.5 m × 2.5 m rectangular glass windowpane that is 0.4 cm thick where the inside temperature is 25°C and the outside temperature is 5°C and Thermal conductivity for the glass is 0.78 W/m/°C

To find : rate of lost of heat through rectangular glass windowpane.

solution : using formula, dQ/dt = KA dT/dx

where K = 0.78 W/m/°C , dx = 0.4 cm = 0.004 m

A = 1.5 m × 2.5 m = 3.75 m²

dT = (5° - 25°)C = -20°C

so, dQ/dt = 0.78 × 3.75 × -20/0.004

= - 14625 W

here negative sign indicates that heat is lost.

Therefore heat lost through the rectangular windowpane is 14625 W

option (A) is nearly equal to gotten answer.

Therefore option (A) 14600 W, is correct choice.