# Get shock from a standard transformer?

Discussion in 'Electronic Basics' started by [email protected], Feb 10, 2006.

1. ### Guest

Hello.
I see on many transformers (of home application like chargers, scanners
etc.) that they're capable of delivering upto 1000ma, or even 1500ma.
As I know, an amount of over 0.24ampre can kill someone.
So how come when I touch both ends of the output (which is about 12v)
nothing happens, I dont get any feeling at all, let alone get zapped to
the next life?

2. ### Pooh BearGuest

Less than that in fact.
The voltage is to low to do any harm. You're probably drawing microamps.

Graham

3. ### Guest

The voltage is to low to do any harm. You're probably drawing microamps.

Can you explain this to me?
Because I know that its the current which counts, like, for instance in
those transparent balls that when you touch them you draw a small
lightning - they contain something like thousands of volts, right? and
they don't electrify you.
Also, where I work they use 24vDC rt amplifiers that go up to 1000w, so
they use 20-30A, and they _can_ shock you, despite the relatively low
24v, right?
so how does it work?

4. ### GotCoffeeGuest

Try wetting your fingers first. If that doesn't work, wet your fingers
with salt water (lick them). Remember to use the same hand for both
leads. You don't want any current running thru your heart.

The 12V is enough voltage. It's the amps that kill. We tell the
people just starting into electronics that 100mA is enough to kill you
if it goes across your heart.

5. ### Guest

Are you saying that if I do that on my transformer I _will_ get zapped?

6. ### Rich GriseGuest

The 1000mA or 1500 mA is what the power supply is _capable_ of providing.
Since it's a constant voltage supply, the current drawn by the load (in
this case, you) is _inversely_ proportional to the resistance of the load,
and the resistance of dry skin is in the tens to hundreds of thousands of
ohms.

Hope this Helps!
Rich

oh ok...
thanx!

8. ### Ralph MoweryGuest

While small ammounts of current (anything over about .05 amps , or 50 ma) is
very dangerous through the outside of the body, it has to do with the
resistance of your skin. Normal dry skin resistance is a few 100, 000s ohms
or more. The 12 volts from the transformer can not force much current
through that resistance. Plug it into the I=e/r equation. That is the most
current that can be drawn from the transformer will be atleast 100,000 ohms
devided by 12 volts. That is way below the .001 amp that it takes for most
people to feel on the outside of the skin. If you apply 12 volts directly
to the heart or brain where it is wet and a short distance apart, then it
may be dangerous. If you take a 9 volt battery and touch it to your mouth
where it is wet and the resistance is much less than 100,000 ohms then
enough current will be drawn to be felt.

You have to understand that no mater how much current a power source can
supply, it is the resistance in the circuit that limiates the current drawn.

9. ### James T. WhiteGuest

Your 12v transformer can deliver up to 1000ma into a load. If you hook
a 12 ohm resistor across the transformer output, the voltage across the
resistor would be 12v and 1000ma would be flowing through it.

Luckily for you, your skin resistance is much, much higher than 12 ohms
so if you touch the terminals only a tiny fraction of 1000ma flows
through your body. As others have suggested, you can increase the
current flow by wetting your hands with water or salt water to reduce
your skin resistance. If you are unlucky enough to break the skin with
the terminals, you would present an even lower resistance.

10. ### Guest

The voltage is to low to do any harm. You're probably drawing microamps.

Can you explain this to me?
Because I know that its the current which counts, like, for instance in
those transparent balls that when you touch them you draw a small
lightning - they contain something like thousands of volts, right? and
they don't electrify you.
Also, where I work they use 24vDC rt amplifiers that go up to 1000w, so
they use 20-30A, and they _can_ shock you, despite the relatively low
24v, right?
so how does it work?

11. ### Guest

pls ignore this message... I sent it about an hour ago :-b

12. ### Bob MastaGuest

In addition to what others have posted, note that at RF
frequencies there may be a greater ability to punch through
the dead skin cells at the surface which are causing the
skin resistance to be so high. So don't mess around with
this!

Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

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