When high energy radiation strikes the Earth from space, it’s called cosmic rays. To be accurate, a cosmic ray is not like a ray of sunshine, but rather is a super-fast particle slinging through space. Think of throwing a grain of sand at a 100 mph… and that’s what we call a ‘cosmic ray’. Build your own electroscope with this video!
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This is the same project, but we’re using it in the context of particle physics.
This seems to be the same lesson as the previous one called Electroscope. Is it supposed to be something different?
In addition to insufficient sanding of the metal wire, another common problem is the weight of the aluminum foil. You want the foil to be as thin (and therefore light) as possible. Try using generic foil, or foil from a dollar store.
If you have a multimeter with a continuity setting, you test the wire and the foil to make sure they are conductive. If a material is electrically conductive, it the continuity test will beep when both meter probes are touching the surface.
Here is a multimeter with a continuity setting: https://www.jameco.com/z/DT830D-3-5-Digit-8-Function-Multimeter-with-Signal-Generator_2230002.html
We followed directions exactly but the aluminum foil leaves are not moving at all. It is a dry day. We sanded the metal wire very thoroughly (it had a white paint coating on it). It sounds like many people in the comments section had the same problem. Has anyone done any more troubleshooting on this and had success?
Oh no! I looks like the last page was not uploaded with the document. I’ll fix this. In the meantime, here are the answers:
1. The foil strips have the same electrical charge, and like charges repel.
2. To discharge the electroscope you can touch it with your hand so the charge runs back into the ground.
3. Glass is an excellent insulator and will not discharge the charge prematurely.
4. Yes.
5. Charged balloon and hair, PVC pipe and brown paper bag, fur against plastic wrap or a glass rod, socks on carpet, skin and polyester clothing, etc.
I downloaded the student worksheets and exercises and there is not an answer key with it. Where can I locate the answer key?
I am not sure what you are thinking – can you please try again so I can answer your question better?
Why can’t you just take off the tinfoil on top of the wire and leave it by itself and touch the wire?/:( it never made sense why.
Hmm, if you can’t see the vapor trails and you only see the mist or smoke, wait another 10 minutes for your system to get really cold. Put your hand on top of the jar to warm it (the side without the dry ice). Did you also turn off the room lights and use a flashlight to shine the beam through the side of the jar? If after waiting still no tracks appear, check to be sure you have an airtight seal. If not, tighten that lid and try again, and you can even add a little more alcohol first. You can also change the position of the jar – sometimes it’s hard to see the tracks in certain positions, so you can place black paper behind the jar so it’s not quite so see-through. If all those tricks don’t help, I would use a larger jar and a different radiation source. Hope this helps!
Hi, we’re trying to do the cosmic ray detector with alcohol and dry ice. Followed to the letter as far as I can tell but didn’t work – no trails at all. Please give some tips to increase the probability of this thing working. Thanks. Jennifer
You need something small and lightweight for the leaves so they can move with the lightest charge.
does any metal work?
Hi Andie! Just one – you need a bare piece of metal to stick through the lid and hold the foil in place. If you use a wire coathanger, be sure to strip off the insulation first, especially if it’s clear!
Hey Aurora, it’s Andie. I was wondering, how many wire coat hangers do you have to have?
I am having trouble understanding your message. Can you be more specific about what the experiment is or isn’t doing? You can even send me a photo or a video so I understand better what’s going on.. it’s hard to figure out when I am not right there next to you. Please let me know how I can help.
ms arora,
we followed all the instux but it does not work, does it not work with a meatal lid
?
A metal lid might dissipate the charge so it won’t build up, but you should still be able to see the leaves stretch apart. Is it humid today where you are? If so, this experiment will not work until the air dries up more.
We tried several times with balloons and socks, but nothing worked.
Is having a metal lid a bad thing?
No, magnetic POLES are totally different from an electric CHARGE. Like charges: plus and plus or a minus and minus will repel each other. Like poles also repel: north and a north side of a magnet will exert a push on each other, for example. The charge on the foil is the same on both halves, so since they are the same, they repel and exert a push on each other. You can either charge the foil with positive or negative charges, depending what you rub and with what.
Human hair tends to give away electrons and become positively charged, so when you touch the ball of the electroscope to your head (after you rub the balloon with it), the foil will be positively charged. If you touch the balloon to it instead (after rubbing it on your head), the will foil be negatively charged.
Why do the two tinfoil flaps open up away from each other when charged? Does it have to do with the north and south ends of a magnet?
This is an electroscope, which is how you can detect beta decay (electrons) in the atmosphere. It’s also something you can use to detect static electricity. I use these in class to teach kids about static charge before we move onto current through a wire, so they understand it’s really the same thing. If it’s not your thing, you can just skip it to move onto something that excites your interest more. 🙂 There’s plenty to choose from!
Hi,
Im trying to figure out why we would need this? Is it anything we could use for practical purposes? Why do scientist use these? What are they used for?
Not magnetized (that’s North-South, like a magnet), but charged (plus-minus). Touch the top ball and it should reset. If not, unscrew the top and curl them away from each other slightly.
Um my aluminum leaves maybe got magnetized or something, because one side attracts each other and one side repulses each other. Is there anything I can do?
Yes – here they are:
1. How does this detector work? (When the particle enters the chamber, it smacks into the alcohol vapor and makes free ions. The vapor in the chamber condenses around these ions, forming little droplets which form the cloud trail.)
2. Do all particles leave the same trail? (No. Different types of particles leave different trails. Alpha particles are heavy and create straight, thick trails. Beta particles, which are light, will leave light, wispy, trails. If you see any curly trails or straight paths that take a sharp turn, those are particles that have smacked into each other.)
3. What happens when the magnet is brought close to the jar? (You can use a magnet to deflect the cosmic rays if the magnet is strong enough and positioned just right.)
Are there answers to the worksheet exercises for this experiment?
You’re right – the video is the wrong one! So sorry about that. We’ve been updated the players any I think my programmer mixed this one up.
I’ve updated it so it’s the correct video now.
The video shows detecting particles using a fog chamber with dry ice, isopropyl alcohol and a jar with felt. Is this the correct video to go with the electroscope handouts?
It sounds like the experiment worked based on your comments here! The foil flaps moved when you brought the balloon next to the foil ball (that’s what is meant by “charging” it… sorry for any confusion around that!)
Discharging means that you touch it with your finger to “ground” the device, which means that there are now not a positive or negative charge on the ball (and also foil strips) so they hang down. When you charge it, you are usually adding more electrons to the ball, and it sounds like the balloon worked the best for you. If you have access to an old CRT TV (the kind of TV with a curved screen), those work REALLY well. We’ve had kids report they’ve slid down a plastic slide with it, brought it near the dryer, and other fun things like this to “detect” large areas of static electricity. 🙂 Hope this helps!
We did this experiment the other day. Let me tell you what we did so you can tell me where we went wrong. We used a large canning jar covered with a piece of paper cut out to fit over the jar, then instead of using a hanger we used 2 small paper-clips twisted tightly together. We then followed the other directions exactly. The foil flaps did, indead, slightly fly apart from each other when the balloon got near the foil.So we knew that it was working. However, after that, the foil simply went back to its original position and did not move againlike the video suggests. We wondered if perhaps we did not understand what it meant to “charge” the device? And I thought perhaps using 2 paper clips was causing it to not work well so we tried using one but that didn’t work at all because it was too top heavy with the foil. So then I decided that we should use a wire hanger (we shaved off all the coating) and made it again. This time we still used paper to cover the jar but we hot glued the hanger in. It worked even worse – the flaps just barely barely moved when we brought the balloon near. It was not humid. Both times, with the paper clip and the hanger, the only thing that even slightly worked was rubbing the balloon on our heads – nothing else that we tried would charge it. Guesses as to what we can change to make it work? Also, the exercise questions were confusing. We had no idea what kinds of other things to do to charge it, and you did not explain what “discharging” meant. There was also a question about magnets but neither the video nor the written instructions mention a magnet. I found this, our first experiment, to be confusing and disappointing.
Yes, discharging means grounded, and you can do this just by touching the foil ball on the top. The all is constantly being hit by charged particles all the time, so you’ll see the foil leaves twitch a bit every 5 to 10 seconds (as long as it’s not too humid or raining). If you rub a balloon on your hair and then bring it close to the ball and you’ll see the leaves move far apart!
How do we discharge the electroscope? how do we ground it? does grounding mean discharging?
Hmm… I am not sure without seeing your experiment in person. Make sure it’s not humid (you’ll want to do this on a warm, dry day) and that the ball is touching the metal rod and the rod is touching the foil strips inside the jar. You shouldn’t have tape between them or it’ll act like an insulator.
There are lots of ways! You can rub a balloon on your head and bring it near the top conductor. 🙂
how do you charge your electroscope?
My electroscope does not work very well. I cant see the parting. Is there a size that the ball needs to be or is the tape a problem? Thanks.
Whoop! That’s the wrong video… I’ll get that fixed in a jiffy. It looks like this one got mixed yo when we upgraded our experiments. Sorry about that!
Hi, I was on the cosmic ray detector page, and I first watched the video, then I opened up the worksheet, but then I noticed that the worksheet and the video are two different things. They are bot labeled ‘Cosmic Ray Detector’, but the worksheet has a bunch of stuff in the materials section that are not in the video, or the instructions. I didn’t read any furthur than that, but they had for example, magnets, rubbing alcohol, heavy gloves, dry ice, none of these things were in the video or the instructions. Do you have a seperate video for it maybe? Any different instructions for the electroscope? Please reply,
Sofia
this looks fun and I’ll have to try it sometime!
Did you get my email about the encore teleclass? We had so many folks excited about the class but missed it that we’re doing it again in a couple days.
And yes, we’re turning the class into a video and posting it to the site – you’ll see it listed under ‘Latest News’ on the main page when it’s up next week.
I missed the teleclass today. Would it be here somewhere?
Yes, look in Lesson 3 – it’s all about relativity.
Oh, and are there any special relativity experiments to try? because the Relativity thing kinda fried my brain….
Oh, okay~ thanks Aurora! It’s funny; I actually already used a ballon that i found.
This is a very tricky experiment, meaning that it’s super-sensitive and easy to over-load so you don’t see the charge. The first challenge is to get the electroscope to work and detect static fields – be sure you can get the foil leaves to flicker and move when you bring it near a static field (like a charged balloon: charge a regular latex balloon by rubbing it on your hair for a minute. It will now have a negative charge.).
Once you’ve verified this works, set the electroscope in a space that’s clear of metal (i.e. don’t put it on the dryer). Outside in the sun is a good choice. Leave it for a minute so it will settle, and then watch for tiny movements with the tinfoil. If you’re in a good spot, you’ll see the foil twitch very slightly as tiny charged particles whack into the metal ball on top. These particles carry a *tiny* amount of charge compared to your hair-rubbed balloon, so be patient!
(i’m not really Hope, i’m her son ^^;)
so i got the electroscope part to work, but i didn’t see any flickering. And by “charged”, do you mean holding the staticky surface next to the wad of tinfoil for an extended amount of time? or is it “charged” when you hear the static make it’s way to the receiver?
Yes.
dose the jar have to be glass????
This one is very tricky – see notes in the project and find someone who’s got a keen eye and a lot of patience.
didn’t work, maybe we didn’t sand enough.
OOOOO! thats a really good idea! I might try that!
You can use any piece of wire you have. Make a mini one out of a large paper clip, perhaps?
Aw, to bad we couldn’t do this! We ran out of wire coat hangers. 🙁
sevy keble 🙂