How Does Distance Affect Photocell Output?

[berkeman]

please. i really need the help. please.im desperate

You have to be kidding. Read back through the thread -- the answers to *all* those questions are in the thread. We're not here to do the work for you, just to point you in the right direction. C'mon, you can do it.

 

[einstein2603]

please please please please please please please please please please please please please please please please please please please please

 

[mezarashi]

Permission to express myself:
"..."

 

[einstein2603]

please guys. please

 

[Hootenanny]

If you could write like 5 lines for each one of those so i have a clear idea of what to do and include.

This is getting very close to doing your coursework report for you, which is something we do not do. We don't mind helping you with any specific problems you are having, things you don't understand etc. but it does sound to me like you want us to write your report for you

Most of the things on your wish list we have disscussed already and the others are readily available if you google (other search engines are available ) the net. If you find something that your not sure about, just come back and ask (or ask you physics tutor as it is his job).

i know berkeman and Hoot, you have helped me so much already...your help has been invaluable so far. thanks

Thank you and your welcome, but it is your turn to do some work now

-Hoot

 

[einstein2603]

just one line for each

 

[bytefire]

This is the Physics OCR planning exercise isn't it. I would be very careful of asking someone else to write this for you especially when it is posted on an internet forum as OCR do check your work against what they find on the internet and I managed to find this post simply by searching "the output of a photocell" in google.

 

[berkeman]

What's the OCR (not optical character recognition, I'm guessing)? Don't worry, us homework helpers here in the Physics & Math Forums won't do his work for him. He was pretty persistent in asking, though...

 

[Hootenanny]

This is the Physics OCR planning exercise isn't it. I would be very careful of asking someone else to write this for you especially when it is posted on an internet forum as OCR do check your work against what they find on the internet and I managed to find this post simply by searching "the output of a photocell" in google.

This is exactly we do not recommend posting full solutions. Einstein take note and heed the warning.

 

[Hootenanny]

What's the OCR (not optical character recognition, I'm guessing)? Don't worry, us homework helpers here in the Physics & Math Forums won't do his work for him. He was pretty persistent in asking, though...

In the UK the OCR is an examination board "Oxford Cambridge and RSA Examinations"

 

[einstein2603]

this thread should be deleted then. TO THE ADMININISTRATORS - DELETE THIS THREAD ASAP.

 

[andrevdh]

Shame on you guys! Just look what you have achieved now. He might have turned out a great scientist. You scared him out of his wits!

We, and your teacher, do not expect original research from you at this stage of your life (but it would be great if you could!). That means you do need to get info from somewhere else, especially if it is not a basic Physics experiment. How you go about getting, interpreting, using and writing it up is more important at this stage. You are also suppose to mention your sources in your report.

 

[Hootenanny]

Shame on you guys! Just look what you have achieved now. He might have turned out a great scientist. You scared him out of his wits!

I didn't wish to scare him, I was simply stating that at PF we don't do people's homework for them and especially not their coursework! Have you seen what he was asking?

for this whole thing, i need:

1. the procedure to be followed
2. how the output of the photocell would be measured
3. range of distances to be used
4. ranges of measuring distances uesd
5. any relevant circuit diagrams
6. any safety precautions
7. particular features which ensure the accuracy and reliability of the results
8. any graphs to be drawn

[...]
If you could write like 5 lines for each one of those so i have a clear idea of what to do and include. That would be great

Regards,
~Hoot

 

[bytefire]

I was just warning him about the fact the exam board does check on the internet. Even if he gave this site as a reference I don't think the exam board would be happy about the fact he kept asking people to write it for him.

Plus if he has asked this on another site and they did what he asked and wrote some for him. If he used this and OCR found out then he would be disqualified from his physics exams at least if not others.

 

[andrevdh]

I agree, but taken into consideration that it is probably his first time attempting something like this one can try and point him in the right direction without scaring him, which most of you did (not the scaring I mean!), but maybe the knowledge gap was still too wide. As educators one should strive to encourage active engagement of the student with the topic - one way or the other. I don't think anyone will be willing to do someone else's homework for free, just pointers will do. I got the impression that he was totally out of his depth.

 

[anapatel]

hiya, i have to do the same piece of work but I want to write a bit about infrared radiation in atmosphere and how that can affect my results. I'm also a bit confused on why i should have a voltmeter in the circuit and not just an ammeter. could anyone help!

thanx

 

[anapatel]

i also would like to know whether the experiment has anything to do with the photoelectric effect.

 

[ekinnike]

ii would like to share my thoughts.Iam in eistein's situation atm. My assignment made me waste a lot alot of hours researching and outcome I am confusing so bad at the same time clear up something and headaches. Sometime u just have to take the short cut way by asking directly:p. Any help would b kindly though. BTW i just went on dis forums few days ago. I wonder where r u people from(the majority). Like i been searching though forums i find things i neva heard b4 or maybe it advance coarse?. I live in Australia>.>

 

[anapatel]

so do you now anything about the work.

england

 

[anapatel]

hiya ekinnike, do you know what you call a point source of radiation- i mean apparatus you'd use for infrared radation source

 

[ekinnike]

hiya ekinnike, do you know what you call a point source of radiation- i mean apparatus you'd use for infrared radation source

hello, sadly i kno hardly any solid physics. Sorry can't help u.

 

[Cheery Blossom]

I think the photocell gives an output due to the photoelectric effect
Anyways...
OI mate (einstein) its exactly what bytefire said right? I found this the same way as bytefire did and this is the planning exercise I've got to hand in on the 17th, u're grateful in a way that u acknowledge the help u're given but at least put it together yourself, u lazy bum.

U are "Lei sai po"

Btw, thanks for the help here, I've gained more than enough background info. Cheers!

 

[bigbadcityboy]

im doing the same experiment, should i explain anything about the photoelectric effect or just mention?

 

[Cheery Blossom]

My teacher said we only need to know the background, so I think I might mention it ie how photocell works..

 

[berkeman]

hiya ekinnike, do you know what you call a point source of radiation- i mean apparatus you'd use for infrared radation source

How about a flame? Like from a Bunsen burner. Or a small light bulb.

 

[lewmang]

Voltmeter?

Hi, I am doing the planning exercise aswell.

Would a voltmeter be ok to measure the output of the photocell because voltage is proportional to resistance ( which varies with amount of infrared radiation shone on it)?
Thanks, Lewis

 

[berkeman]

Hi, I am doing the planning exercise aswell.

Would a voltmeter be ok to measure the output of the photocell because voltage is proportional to resistance ( which varies with amount of infrared radiation shone on it)?
Thanks, Lewis

No, you can't use a voltmeter directly. You can put an explicit resistor in series with the photodiode, and measure the voltage drop across the resistor from the photocurrent.

Check the accuracy and sensitivity specs for your DVM, and check the specs for the output photocurrent that you expect from your photodiode/photocell. Then figure out which method will give you the best data...

 

[lewmang]

thanks for the quick reply.
Ok, so ill use a fixed resistor in series with the LDR, would an LDR pick up infrared radiation?
And what kind of voltage would be needed to put through the currents.
By the way i don't hav to actually do the experiment i have to design it with some theory as evidence for my actions.

 

[lewmang]

*wht kind of voltage would be needed to send through the circuits

 

[berkeman]

I didn't say use a resistor in series with a Light Dependent Resistor. As for the IR sensitivity of LDRs, I have no idea. As part of your project, you need to find and read the datasheets for the various light sensing component technologies, and list the advantages and disadvantages of each. That will guide your choice as to which one to use for the IR sensor experiment.

 

[lewmang]

what do you mean by datasheets? We havn't been given any data to use it is basically start from scratch

 

[berkeman]

what do you mean by datasheets? We havn't been given any data to use it is basically start from scratch

Use the Internet. Use google some, look for companies that manufacture the components that you are considering, download the PDF datasheets for the components, and start reading the specifications. That's how it works in the real world after school...

Like, I just googled +photodiode +IR and got lots of hits. Here's the first one:

http://photodiode.globalspec.com/Industrial-Directory/photodiode_ir

 

[lewmang]

I read earlier on in the thread that you said maybe use a small balb, would this be sufficient too?

 

[lewmang]

what kind of photocell would be needed to measure infrared radiation that would be available in schools?

 

[berkeman]

What do you mean by "available"? You mean like what can you take apart to pull out a photocell for experiments (like an elevator door sensor, or somebody's camera light sensor)? Won't you get in trouble if you start taking things apart at school? Or do you mean some part that is easy to order from a place like Digikey.com?