Question

A refrigerator has a power of 90 w and is left on for 24 hours. A hair dryer has a power of 900 w an is on for 20 minutes. Which statement correctly compares the energy used by these devices

Answer 1

The refrigerator has consumed more energy

Explanation:

The relationship between power and energy consumed by a device is given by

$E=Pt$

where

E is the energy

P is the power

t is the time elapsed

For the refrigerator, we have

P = 90 W

$t = 24 h \cdot 3600 = 86400 s$

Therefore the energy consumed is

$E=(90)(86400)=7.78\cdot 10^6 J$

For the hair dryer, we have

P = 900 W

$t = 20 min \cdot 60 = 1200 s$

Therefore the energy consumed is

$E=(900)(1200)=1.08\cdot 10^6 J$

Therefore, the refrigerator has consumed more energy.

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