Physics, 29.08.2019 23:30 edjiejwi

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?

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Answer from: kimlyn58p0wyn0

a) There must be 8 LED's combined into one ligth source to give a total of 1.6W of visible-light output.

b) The total power necessary to run this LED lightsource is 8.0W

Explanation:

a) According to this problem, each white LED will have an efficiency of 20%. This means that each LED will use only 20% of all the inputed power and turn it into visible light. The rest of the power will turn into heat loss.

So taking this into account, let's take the total amount of power each LED will consume and let's multiply it by it's efficiency.

$P_{converted}=P_{consumed}*N$

Where N is the efficiency, so we get:

$P_{converted}=1.0W*0.20=0.20W$

So from this equation we know now that each LED will turn 0.20W of the energy consumed into light.

Once we have this data we can use conversions to find the number of LED's needed to give a total of 1.6W of visible-light output. So we get:

$1.6W*\frac{1LED}{0.2W}=8LED's$

So the we need 8 LED's to get a total of 1.6W of visible-light output.

b) Since we need 8 LED'S on our lightsource and we know that each LED will consume a total of 1.0W, then all we need to do is multiply the number of LED's by the number of Watts consumed to get the total of Watts consumed by the LED's.

$P_{total}=8LED's*\frac{1.0W}{1LED}=8.0W$

So the total power necessary to run this LED lightsource is 8.0W

Answer from: Quest

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this. hope that you like the video and that it explains more in detail to you.

that is the link.

Answer from: Quest

massxgravity x heght=weightxheight= pe

4900=490xh

h=10

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An individual white led (light-emitting diode) has anefficiency of 20% and uses 1.0 w of electric po...