physics help (1 Viewer)

[speed_bump]

can anyone tell me how is the photoeelectric effect used in solar cells, photocells and breathalysers?????

 

[wogboy]

Basically, a solar cell works by having two pieces of semiconductor material (commonly silicon) next to each other, one of the is p-type (excess holes, deficient in electrons) and the other is n-type (excess holes). As sunlight (photons) strikes the n-type semiconducter, electrons are ejected in accordance with the photoelectric effect to the p-type semicondutor and an emf is induced between these two semiconductor types, and if they are short circuited with an external circuit (load) then a current flows.

A photocell is basically a piece of semiconductor material that conducts better when in the presence of light, since the electrons are moved into the conduction band by the incoming photons as per the photoelectric effect.

Breathalysers contain a certain mixture of sulphuric acid, silver nitrate, potassium dichromate, and water. As alcohol mixes with these chemicals, they change colour from orange to green depending on the alcohol concentration that has been dissolved into it. A photocell is then used to measure this colour change, and report it on the display of the breathalyser.

For more info, check out these websites:

http://science.howstuffworks.com/breathalyzer.htm
http://science.howstuffworks.com/diode.htm
http://science.howstuffworks.com/solar-cell.htm
http://www.infoplease.com/ce6/sci/A0845833.html
http://www.infoplease.com/ce6/sci/A0838866.htm

 

[+:: $i[Q]u3 ::+]

i thought we didn't have to learn breathalysers?
haven't they been cut out of the syllabus?

 

[ND]

It's for a research assignment (i'm in speed_bump's class). Stuey i think research involves a little more than a quick trip to the BOS forums.

 

[McLake]

Originally posted by ND
It's for a research assignment (i'm in speed_bump's class). Stuey i think research involves a little more than a quick trip to the BOS forums.

I don't see why ...

 

[ND]

Originally posted by McLake


I don't see why ...

It's an assessment with a weighting of 15% (or is it 20?).

 

[+:: $i[Q]u3 ::+]

ahh i see =)

our school only gives research assignments that are directly quoted from the syllabus; if it aint in the syllabus, we don't know it.