Q14 of 19 Page 374

Two bulbs of 40W each are lighted for eight hours daily. Find the cost of electrical energy consumed by them in one week at Rs. 3 per unit.

Given

Power = 40W


Time = 8 hours


Now


Power =


⇒


⇒ Energy =


Energy consumed by 2 bulbs in 1 week = 320×2×7 = 4480 Wh = 4.48 kW


(∵ 1kWh = 1000Wh)


Total units = 4.48 units


Now


Cost of 1 unit = Rs 3


Total cost = 4.48 ×3 = Rs13.44


Total cost for 1 week is Rs 13.44


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