P27_033.PDF

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Chapter 27 - 27.33

33. (a) Electrical energy is converted to heat at a rate given by

P = V 2

R ,

where V is the potential diﬀerence across the heater and R is the resistance of the heater. Thus,

P = (120V) 2

14 Ω

=1 . 0

10 3 W=1 . 0kW .

(b) The cost is given by

(1 . 0kW)(5 . 0h)(5 . 0cents / kW

h) = 25 cents .