In a certain city, electricity costs $0.13 per kw·h.
what is the annual cost for electricity to power a lamp-post for 7.50 hours per day with (a) a 100.-watt incandescent light bulb (b) an energy efficient 25-watt fluorescent bulb that produces the same amount of light? assume 1 year = 365 days.
(a) 100.-watt bulb
(b) 25-watt bulb

Part a)

cost = $35.58

Part b)

cost = $8.89

Explanation:

Part a)

Annual cost of the incandescent light bulb

Power = 100 Watt

daily use = 7.5 hours

total use of one year

cost of energy = $0.13 per kWh

so total cost of energy = $0.13 (273.75)

cost = $35.58

Part b)

25 watt fluorescent bulb

Power = 25 Watt

daily use = 7.5 hours

total use of one year

cost of energy = $0.13 per kWh

so total cost of energy = $0.13 (68.437)

cost = $8.89

when it gains or loses electrons

this could be newton#'s law of cooling. the cooling curve is exponential