A room has AC run for 5 hours a day at a voltage of 220V. The wiring of the room consists of Cu of 1 mm radius and a length of 10 m. Power consumption per day is 10 commercial units. What fraction of it goes in the joule heating in wires? What would happen if the wiring is made of aluminium of the same dimensions?
Total energy consumed in 5 hrs a day by AC and wiring =10kWh ∴ Energy consumed in 1hr by AC and wiring =2kWh So total power of AC and wire =2000W P=VI I=VP=2202000≅9.0A Let P0 is power of wiring then, P0=I2RW[RW= resistance of wiring ] =9×9⋅Aρ! =3.14×1×10−3×1×10−39×9×1.7×10−8×10=3.1481×17×10−8+6 =3.141377×10−2=4.38=4.4Watt So loss of energy in wiring ≅4.4J/sec The dfractional loss due to heating of wires =20004.4×100%=0.22% PCu(wiring)PA(wiring)=I2RCuI2RA=ρCuACulCuρAiAAilAas1Al=LCu and
