JAMB - Physics (2020 - No. 13)
What is the cost of running five 50W lamps and four 100W lamps for 10 hours if electrical energy costs 2 Kobo per KWh?
N0.65
N0.39
N3.90
N0.13
Explanation
POWER = energy consumed/time
Energy consumed = power x time
energy consumed = \(\frac{(5 \times 50) + (4 \times 100) \times10}{1000}\)
= 6.5KWh.
but 1KWh = 2kobo
then 6.5KWh = 6.5 x 2 = 13kobo →#0.13
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