An electric heater is placed inside a room with total wall area to maintain the…

PHYSICS · Subjective · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter

Problem

An electric heater is placed inside a room with total wall area 137 m2137\,\text{m}^2 to maintain the inside temperature at 20∘C20^\circ\text{C}. The outside temperature is −10∘C-10^\circ\text{C}. The walls have three layers: an innermost wood layer of thickness 2.5 cm2.5\,\text{cm}, a cement layer of thickness 1 cm1\,\text{cm}, and an exterior brick layer of thickness 2.5 cm2.5\,\text{cm}. Find the power of the electric heater, assuming no heat loss through the floor and ceiling. The thermal conductivities of wood, cement, and brick are 0.125 W m−1 ∘C−10.125\,\text{W m}^{-1}\,{}^\circ\text{C}^{-1}, 1.5 W m−1 ∘C−11.5\,\text{W m}^{-1}\,{}^\circ\text{C}^{-1}, and 1.0 W m−1 ∘C−11.0\,\text{W m}^{-1}\,{}^\circ\text{C}^{-1} respectively.

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