Part A How many LEDs must be combined into one light source to give a total of 2

Question

Part A

How many LEDs must be combined into one light source to give a total of 2.0 W of visible-light output (comparable to the light output of a 60 W incandescent bulb)?

Part B

What total power is necessary to run this LED light source?

An individual white LED (light-emitting diode) has an efficiency of 20% and uses 1.0 W of electric power.

You may want to review ( pages 319 - 322) .

Part A

How many LEDs must be combined into one light source to give a total of 2.0 W of visible-light output (comparable to the light output of a 60 W incandescent bulb)?

Part B

What total power is necessary to run this LED light source?

Explanation / Answer

If the efficiency is 20% then 5W of electrical power gives 1 W of light power

and 10W of electrical power will give 2 W of light power.

So the answer is N = 10 LEDs and 10W of electrical power.

So:

A) 10

B) 10W

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