A device converts 90% of electrical energy into useful energy (light). What is its efficiency?

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Multiple Choice

A device converts 90% of electrical energy into useful energy (light). What is its efficiency?

Efficiency is the proportion of input energy that becomes useful output, shown as a percentage. If 90% of the electrical energy is converted into light, that means the device uses 90% efficiency. For every 100 units of energy put in, about 90 units come out as light, and the remaining 10 units are lost as other forms such as waste heat. The other numbers (80%, 100%, 70%) don’t match the stated 90% conversion, so they’re not correct.

Efficiency is the proportion of input energy that becomes useful output, shown as a percentage. If 90% of the electrical energy is converted into light, that means the device uses 90% efficiency. For every 100 units of energy put in, about 90 units come out as light, and the remaining 10 units are lost as other forms such as waste heat. The other numbers (80%, 100%, 70%) don’t match the stated 90% conversion, so they’re not correct.

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