Mylar sheet, 1 sq foot charged to 20 KV, clap to discharge

In summary, the conversation discusses a potentially dangerous experiment that took place in school many years ago involving charging a mylar sheet with a high voltage and discharging it through contact with the hands. The individual involved felt a compression in their chest but was not sure about any potential brain damage. They attempted to calculate the energy discharged, but there were some uncertainties with the calculations. The teacher responsible for the experiment was deemed irresponsible and possibly should have faced consequences.
  • #1
smokingwheels
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Please delete if not allowed.

The teacher charged a 1 square foot sheet of mylar sheet up to approx DC 20 kv one day long ago in school via an modified EHT output of a TV.
I had one of my mates hold it by the corners in line with my hands, I then judged and guessed and clapped it with both hands opposite sides to discharge it.
I felt the compression thru my chest my heart seemed to sort itself out and that was 30 years ago.

Not too sure about brain damage?
I was never that good at basic school work anyway.

Calculation.
I am not sure about the contact closure time of hands (2 mS).
Full Hand to Hand resistance unsure (1 k).
Surface area of hand .054 m square.
Mylar sheet dielectric constant 3.1, thick enough to withstand 20 kv.

I have come up with 1.186 Joules or 600 W roughly discharged.
 
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  • #2
You have big hands -- or did you add the two sides ?
care to show your calculation ? You left out the mylar thickness
Looks as if teacher should be in jail -- still.
 
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  • #3
Lets say I have average hands with slightly longer fingers but skinner.
I used 1st result in Google "Surface area of hand" so no I only used one plate.
Calculation well Googled across 2 OS ..copy and past has a problem from Raspberry Pi Pixel OS to Ubuntu Thinlinc Server so can't post all the links to the online caluclators..
Mylar thickness I did say "thick enough to withstand 20 kv." maybe I should of added with corona activity on insulation brake down.
The Teacher did check my condition a few minutes later and I said, Yes I am fine so I guess that covers him...
 
  • #4
smokingwheels said:
I used 1st result in Google "Surface area of hand" so no I only used one plate
Surface area of hand is what gets wet when you submerge it. The contact area with the mylar is much smaller.

How does teacher put charge on a mylar sheet ? Is the surface conducting somehow ? Or does he just rub it on ?
smokingwheels said:
Calculation well Googled across 2 OS ..copy and past has a problem from Raspberry Pi Pixel OS to Ubuntu Thinlinc Server so can't post all the links to the online caluclators..

?

You did something like ## Q = CV ##

with ##C =\displaystyle {\varepsilon_0 \varepsilon_r A \over d } ##

so, say ##C\approx \displaystyle{3.1 \ 8.9\,10^{-12} \ 0.054 \over 50\, 10^{-6} }\ = 30 ## nF

(for a 50 ##\mu## thick sheet)

and Q ## \approx 0.0006 ## C ?

So that ##E = {1\over 2} CV^2\approx 6 ## J ?
 
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  • #5
BvU said:
Looks as if teacher should be in jail -- still.
No kidding, what an idiot.

@smokingwheels -- You would need the thickness of the Mylar sheet and its area. I'm assuming it had metalization on both sides, and it was charged up like a capacitor. You calculate the capacitance using a simple formula that you can look up, involving the area, thickness and dielectric constant. Clapping it with your hands give you an arm-to-arm shock, which is extremely dangerous. You were lucky your heart didn't go into ventricular fibrillation. Thread is done.

EDIT -- I see BvU helped you with the calculations. Thanks BvU. :smile:
 
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FAQ: Mylar sheet, 1 sq foot charged to 20 KV, clap to discharge

What is a Mylar sheet?

A Mylar sheet is a type of polyester film that is commonly used for its strength, durability, and electrical insulation properties. It is also known as BoPET (biaxially-oriented polyethylene terephthalate) and is often used in packaging, electronics, and other industrial applications.

What does it mean to charge a Mylar sheet to 20 KV?

Charging a Mylar sheet to 20 KV means that the sheet has been given an electrical charge of 20,000 volts. This can be done using an external power source or through a process called triboelectric charging, where two materials are rubbed together to create a static charge.

Why would someone want to charge a Mylar sheet to 20 KV?

Charging a Mylar sheet to a high voltage can cause it to become electrostatically attractive, meaning it can attract and hold onto particles or objects with opposite charges. This property is often used in industrial processes such as electrostatic painting and filtration.

What happens when you clap to discharge a Mylar sheet charged to 20 KV?

When you clap near a charged Mylar sheet, the sudden movement of air molecules creates a small shock wave that can cause the sheet to discharge its electrical charge. This can result in a visible spark or crackling sound.

Is it safe to clap to discharge a Mylar sheet charged to 20 KV?

Generally, it is safe to clap to discharge a Mylar sheet charged to 20 KV as long as you are not in direct contact with the sheet. However, it is always important to use caution when working with high voltages and to follow proper safety protocols to prevent electric shock.

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