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

  • #1
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 its self 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.
 

Answers and Replies

  • #2
BvU
Science Advisor
Homework Helper
14,480
3,752
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.
 
  • Like
Likes smokingwheels
  • #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 cant 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
BvU
Science Advisor
Homework Helper
14,480
3,752
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 ?


Calculation well Googled across 2 OS ..copy and past has a problem from Raspberry Pi Pixel OS to Ubuntu Thinlinc Server so cant 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 ?
 
  • Like
Likes smokingwheels
  • #5
berkeman
Mentor
60,371
10,664
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:
 
  • Like
Likes smokingwheels

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

  • Last Post
Replies
3
Views
3K
Replies
2
Views
897
  • Last Post
Replies
4
Views
4K
Replies
8
Views
1K
Replies
1
Views
771
  • Last Post
Replies
17
Views
6K
  • Last Post
Replies
4
Views
1K
Replies
24
Views
4K
Replies
4
Views
11K
Top