What is the percentage decrease in the consumption of energy by an electric lamp marked 60 W 200 V if it is worked at 110 V?
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Answer:
Answer
Correct option is
A
decrease
Given power of bulb =60W
Voltage=220V
Power =
R
V
2
60=
R
220×220
R=(
60
220×220
)Ω
R=(
6
220×22
)Ω (1)
When voltage = 200V, resistance will be the same
P=
R
200×200
From 1,
=
220×22
200×200×6
22×22
200×20×6
=49.5W
We see that power gets decreased.
Power means rate of consumption of energy, so rate of consumption of energy decreases.
Option A is correct.
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