A family uses 8 kW of power. (a) Direct solar energy is incident on th

1.	A family uses 8 kW of power. (a) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy how large an area is needed to supply 8 kW? (b) Compare this area to that of the roof of a typical house.
Answer» (a) Let the area be A m² Average power per square meter = 200 W Useful electrical energy produced per square meter, = 20/100 x 200 = 40 Watt Energy required by the family = 8 kW = 8000 watt Hence, A = 8000/40 = 200 m² (b) This area is comparable to that of a roof of a house of 14 m x 14 m.

A family uses 8 kW of power. (a) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy how large an area is needed to supply 8 kW? (b) Compare this area to that of the roof of a typical house.

Answer»

(a) Let the area be A m²

Average power per square meter = 200 W

Useful electrical energy produced per square meter,

= 20/100 x 200 = 40 Watt

Energy required by the family = 8 kW = 8000 watt

Hence, A = 8000/40

= 200 m²

(b) This area is comparable to that of a roof of a house of 14 m x 14 m.