You want to compare the energy efficiency of two electric fans. For every 100 J of electrical energy supplied:Fan 1 produces 60 J of kinetic energy, 30 J of heat and 10 J of sound.Fan 2 produces 85 J of kinetic energy, 10 J of heat and 5 J of sound.Determine which fan is more efficient.Fan 1Fan 2
Question
You want to compare the energy efficiency of two electric fans. For every 100 J of electrical energy supplied:Fan 1 produces 60 J of kinetic energy, 30 J of heat and 10 J of sound.Fan 2 produces 85 J of kinetic energy, 10 J of heat and 5 J of sound.Determine which fan is more efficient.Fan 1Fan 2
Solution
The efficiency of a device can be determined by comparing the useful output energy (or power) to the total input energy (or power). The device that converts the highest percentage of input energy into useful output energy is considered the most efficient.
For Fan 1: The useful output energy is the kinetic energy, which is 60 J. The total input energy is 100 J. Therefore, the efficiency of Fan 1 is 60/100 = 0.6 or 60%.
For Fan 2: The useful output energy is the kinetic energy, which is 85 J. The total input energy is 100 J. Therefore, the efficiency of Fan 2 is 85/100 = 0.85 or 85%.
Comparing the two efficiencies, Fan 2 is more efficient than Fan 1 because it converts a higher percentage of input energy into useful kinetic energy.
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