A room has AC run for 5 hours a day at a voltage of 220 V. 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 ?
[ρCu = 1.7 × 10–8 Ω m, ρAl = 2.7 × 10–8 Ω m]
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12th
Physics
Current Electricity
Electric Energy and Power
A room has AC run hours a d...
PHYSICS
A room has AC run hours a day at a voltage of 220V. The wirng of the room consists of Cu of 1mm radius and a length of 10m. Power consumption per day is 10 commercial units . The fraction of it goes in the joule heating in wires is: ρ
cu
=1.7×10
−8
Ωm
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ANSWER
Power consumption =
5hour
10units
=
hour
2units
=2kw
=2000J/S
So, I=
V
P
=
220
2000
=9.09A
Power loss in copper wire =I
R
=I
2
A
PL
Power loss in copper wire =9.09×9.09×
17×(10
−3
)
2
1.7×10
−8
×10
=4.47J
=
2000
4.47
×100%
=0.22%
Power loss in aluminium wire =I
2
R=I
2
A
PL
Power loss in copper wire =9.09×9.09×
17×(10
−3
)
2
2.7×10
−8
×10
=7.1J
=
2000
7.1
×100%
=0.355%
Hence, the answer is 0.355%.