Page 41 - CHAPTER-1 (Electricity)
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CHAPTER 1
ELECTRICITY
Example 14:
An electric fan runs from the 220V mains. The current flowing through
it is 0.6A. At what rate is the electrical energy transformed by the fan?
How much energy is transformed in 2 min?
Solution:
Given, potential difference, V=220V; Current I=0.6A; Time t=2min=120s
Power = ?
We know that,
P=VI=220×0.6=132W
E=Pt=132×120=15840J
So, the power of fan is 132 W and it transforms 15840 J of energy.
Example 15:
An electric refrigerator rated 500 W operates 6 hours/day. What is the
cost of the energy to operate it for 30 days at ₹4.5 per kWh?
Solution:
Energy consumed by refrigerator in 30 days
hours
=500W×6 ×30days
day
=90000Wh
=90kWh
∴ Cost of energy to operate the fridge for 30 days
=90 kWh×₹4.5 per kWh
=₹405
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