Leaf electroscope discharges immediately after contact

[msr777]

Hi all

I've just had a couple of new leaf electroscopes delivered to a school here, bought cheaply online.

They deflect and charge very well but discharge almost immediately when contact is broken. Is this to do with the humidity in my room? If so, would it help to:
use tape to seal where the glass windows slot in?
use one of those silica drying sachets inside before sealing?

Thanks for any advice!

Sorry if this is inappropriate here, but it's the first place I thought of for quick advice.

 

[berkeman]

Welcome to PF.

use one of those silica drying sachets inside before sealing?

That would seem to be a good thing to try. You could even try drying rice in an oven and then quickly putting that into the bottom of the jar and sealing it. Can you upload a picture of the jars? (use the "Attach files" link below the Edit window)

 

[kuruman]

You might also consider cleaning the conducting disk or ball on top of the electroscope with acetone to remove any gunk that might have collected there.

 

[msr777]

Thanks for your replies! Sorry for the delay in responding, end of term and a bit snowed under here.

@berkeman - yes, I'll upload some photos later.
@kuruman - thanks - yes, I have some acetone to clean with.

FWIW I ordered 2 types - a small one in a perspex case with a disc on top and a better, glass cased one with a ball on top. I think the (cheap) perspex one is giving me problems because the charge seems to collect on the perspex itself - I can remove the rod, discharge it and when i replace it, it immediately deflects again. The glass one is of course better BUT since it's to demonstrate the photoelectric effect I need to be able to balance a zinc plate on top. I've managed this by swopping the discs from the cheap one into the glass one and IT WORKS!!!! My cheap UV torch bought from an Ali-express equivalent actually works!!!!

I'm struggling to charge by contact without it immediately discharging, but charging by induction is working. Oddly I can't find the standard perspex and plastic rod set anywhere in this school but a balloon is working very well, rubbed on a plastic ruler so that I can use either to get the right charge on the electroscope. Of course, I have no idea what charge I have until I see whether it reacts to the UV lamp or not.

Photos to follow

 

[Herman Trivilino]

Teaching here on the gulf coast, humidity has been the bane of my electrostatics demonstrations and student experiments. In grad school the seasoned professor kept a small incandescent light bulb on at all times in the cabinet used to store electrostatic demo equipment.

I have tried everything with varying degrees of success. The best strategy is to wait for a low-humidity day. Having kept the equipment in that cabinet means it's ready to go on those days.

The best charging method I've found is the electrophorus. Use this device to charge your electroscopes.