The cost per B.O.T unit of electrical energy is ₹6. Calculate the total cost of electricity used in a month of 30 days if ten 50 W bulbs are used for 10 hours daily. [3]
WBBSE
Class X
Physical Science
Current Electricity
03 Mark
2026
Number of bulbs = 10
Power of each bulb = 50 W
Total power (P) = 10 × 50 = 500 W = 0.5 kW
Time used per day = 10 hours
Total time in 30 days (t) = 10 × 30 = 300 hours
Electrical energy consumed = 0.5 × 300
= 150 kWh = 150 B.O.T units
Total cost = 150 × 6 (Cost per unit = ₹6)
= ₹900
Hence, the total cost of electricity for 30 days is ₹900.
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