Question

A window pane has a thickness 0.5 cm and area 0.8 m^2. The temperature difference between outside and inside surface is 20°C. The rate of heat flow through the pane is ( Thermal conductivity of glass being 0.8J/s m k)
a)2.56 KJ/s
b)3.80KJ/s
c)4.50 KJ/s
d)521J/s

Answer 1

Answer ⇒ Option (a). 2.56 KJ/s or 2.56 W.

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Given conditions ⇒

Thickness of the window pane(l) = 0.5 cm. = 0.005 m.

Area  = 0.8 m²

Temperature difference(ΔT) = 20 °C or 20 K.

Thermal Conductivity (K) = 0.8 W/mk

Using the formula,

Power = KAΔT/l

∴ Power = 0.8 × 0.8 × 20/0.005

∴ Power = 2560 W.

∴ Power = 2.560 kW.

Hence, Option (a). is correct.

Hope it helps.