In a particular area of the country, electrical energy costs $0.12 per kilowatt-hour. (Round your answers, in dollars, to at least two decimal places.) (a) How much does it cost to operate an old-style incandescent 100-W light bulb continuously for 24 hours? $ (b) A modern LED light bulb that emits as much visible light as a 100-W incandescent only draws 16.0 W of power. How much does it cost to operate this bulb for 24 hours? $ (c) A particular electric oven requires a potential difference of 220 V and draws 20.0 A of current when operating. How much does it cost to operate the oven for 5.30 hours? $

a) cost = $ 0.29 , b) cost = $ 0.046 ,  c) cost = $ 2.80

Explanation:

a) Let's find the energy consumed by this bulb, which is the product of the power and time

         energy = P t

         energy = 100 24 = 2400 W h

as the cost of energy is given in kWh we reduce this value

         Energy = 2400 Wh (1 kW / 1000W)

         Energy = 2.40 kWh

Calculate the cost of energy

           cost = 0.12 2.40

           cost = $ 0.288

           cost = $ 0.29

b) energy = 16.0  24 = 384 Wh

we reduce to kWh

      energy = 0.384 kWh

      cost = 0.12 0.384

      cost = $ 0.0461

      cost = $ 0.046

c) let's find the power consumed by the oven

       P = I V

       P = 20.0 220

       P = 4400 W

we look for the energy consumed

       energy = 4400  5.30

       energy = 23320 Wh

we reduce to kWh

       energy = 23.32 kWh

we calculate the cost of this energy

       cost = 0.12 23.32

       cost = $ 2,798

       cost = $ 2.80

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