WBBSEClass XPhysical ScienceCurrent Electricity03 Mark2026 Moderate

QQuestion

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]

Exam-ready answer 03 Mark

Answer

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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