A lamp converts 90% of electrical energy into light. If 200 J of electrical energy is supplied, how much light energy is produced?

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Multiple Choice

A lamp converts 90% of electrical energy into light. If 200 J of electrical energy is supplied, how much light energy is produced?

Energy efficiency tells us how much of the input energy is turned into light. If 90% of the electrical energy becomes light, you multiply the input energy by 0.90. So with 200 J supplied, the light energy produced is 0.90 × 200 J = 180 J. This matches the given efficiency. The other numbers would correspond to different efficiencies: 90 J is 45% of 200 J, 200 J would be 100% efficiency, and 160 J is 80% efficiency, none of which fit the 90% stated.

Energy efficiency tells us how much of the input energy is turned into light. If 90% of the electrical energy becomes light, you multiply the input energy by 0.90. So with 200 J supplied, the light energy produced is 0.90 × 200 J = 180 J. This matches the given efficiency.

The other numbers would correspond to different efficiencies: 90 J is 45% of 200 J, 200 J would be 100% efficiency, and 160 J is 80% efficiency, none of which fit the 90% stated.

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