Engineers who design battery-operated devices such as cell phones and MP3 players try to make them as efficient as possible. An engineer tests a cell phone and finds that the batteries supply 10,000 J of energy to make 5500 J of output energy in the form of sound and light for the screen. How efficient is the phone?

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2 December, 07:08

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Bryce Kline · Answer 1

efficiency = [useful energy transferred : total energy supply]*100%

So, [5500:10000]*100%=0.55*100

=55%