One lightbulb is marked \"29 W 120 V,\" and another \"106W 120 V\"; this means t

Question

   One lightbulb is marked "29 W 120 V," and another "106W 120 V"; this means that each converts its respective power whenplugged into a constant 120 V potential difference.
(a) Find the resistance of each bulb.
R29 = ________
R106 = ________

(b) How long does it take for 1.00 C to pass through the dimbulb?
___________ s

(c) How long does it take for 1.00 J to pass through the dimbulb?
___________ s


(d) Find the cost of running the dim bulb continuously for31.0 days if the electric company sellsits product at $0.0700 per kWh.
$ _____________


What is its price for one SI unit of this quantity?
$ ____________ /Joule (a) Find the resistance of each bulb.
R29 = ________
R106 = ________

(b) How long does it take for 1.00 C to pass through the dimbulb?
___________ s

(c) How long does it take for 1.00 J to pass through the dimbulb?
___________ s


(d) Find the cost of running the dim bulb continuously for31.0 days if the electric company sellsits product at $0.0700 per kWh.
$ _____________


What is its price for one SI unit of this quantity?
$ ____________ /Joule

Explanation / Answer

a) We know that                 R = V2 / P     ==> R29 = 120 * 120 / 29 = 496.55     ==. R106 = 120 * 120 / 106 =135.84 b) We know that                Q = it              ==> t = Q / i = Q R29 / V = 1.00 * 496.55/ 120 = 4.137 s       c)        t = 1.00 *135.84 / 120 = 1.132 s d) E = Pt = 29 * 31 days = 29 * 31 * 24 * 60 *60 = 77673600 J          ==> Cost = E * 0.07 / kWh = 77673600 * 0.07 /3600000 = $1.510 e)     E = 106 * 31days = 283910400 J                 Cost = 283910400 * 0.07 / 3600000 = $5.52

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