A blow-dryer and a vacuum cleaner each operate with a voltage of 120 V. The current rating of the blow-dryer is 13 A, while that of the vacuum cleaner is 4.8 A. Determine the power consumed by (a) the blow-dryer and (b) the vacuum cleaner. (c) Determine the ratio of the energy used by the blow-dryer in 15 minutes to the energy used by the vacuum cleaner in 40 minutes.

(a) 1560 W

(b) 576 W

(c) 1.01

Explanation:

Voltage, V = 120 V

Current in dryer, I = 13 A

current in vacuum cleaner, i' = 4.8 A

(a) Power consumed by dryer,

P = V I = 120 x 13 = 1560 W

(b) Power consumed by vacuum cleaner

P' = V I' = 120 x 4.8 = 576 W

(c) Energy consumed by dryer

E = P x t = 1560 x 15 x 60 = 1404000 J

Energy consumed by the vacuum cleaner

E' = P' x t' = 576 x 40 x 60 = 1382400 J

the ratio of energies is

E : E' = 1404000 : 1382400 = 1.01

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