Question

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

a) How many LEDs must be combined into one light sourceto give a total of 1.6 W of visible-light output (comparableto the light output of a 40 W incandescent bulb)?

b) What total power is necessary to run this LED lightsource?

Answer 1

.

Problem statement: An individual white LED(light-emitting diode) has an efficiency of 20% and uses 1.0 Wof electric power.
a) How many LEDs must be combined into one light source togive a total of 1.6 W of visible-light output (comparable tothe light output of a 40 W incandescent bulb)?
b) What total power is necessary to run this LED lightsource?

.

01.   Each LED is emitting 0.2 Watts of light forevery 1.0 Watts consumed (20.0%).

02.   Quantity = (1.6 Watts)/(0.2 Watts/LED) =8 LEDs

03.   Power = (8 LEDs)*(1.0 Watts/LED) =8.0 Watts

.