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 produce 5,500 J of output energy in the form of sound and light for the screen.
How efficient is the phone?
Answer (3)
efficiency= [useful energy transferred ÷ total energy supply]×100%
So, [5500÷10000]×100%=0.55×100
=55%
The efficiency of a device is calculated by dividing the output energy by the input energy and then multiplying by 100 to get a percentage. In the case of the cell phone, the output energy is 5500 J and the input energy is 10,000 J.
To calculate the efficiency, use the formula: Efficiency (%) = (Output Energy / Input Energy) × 100. Plugging in the values we have: Efficiency (%) = (5500 J / 10,000 J) × 100, which results in 55% efficiency.
The efficiency of the cell phone's batteries is calculated to be 55%, indicating that 55% of the energy is converted into useful output while 45% is lost. This is determined by using the formula for efficiency with the given input and output energy values. Such efficiency is important for ensuring better performance and longer battery life.
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