I'm new to electronics, and I can't make sense of this video. At the 9:10 second mark, he holds a metal spoon across the ends of a wire that's carrying around 100 amps, and he's not harmed. Later the same setup produces over 400 amps, the spoon glows hot while he's holding it bare handed, and he's not shocked.
ElectroBOOM: Making millions of amps of current
How is he not shocked or harmed by this?
WARNING : WHAT THIS GUY DOES IS VERY DANGEROUS
The voltage is very low (<2V), so there is no risk of being shocked (at least not on the secondary side, the 120V on the primary side are plenty enough to get shocked).
Current is dangerous when crossing the human body, but at such low voltage, there is no way to push any significant current across the human body (nb : 30mA can already be deadly).
However, such high currents as he is generating are very dangerous :
When working with any circuit capable of high current, you are supposed to wear appropriate heavy protective equipment (heavy leather clothing, face mask, ...).
So the only risk of electrical shocks is from the primary side. But the secondary side is still very dangerous due to the high current (burns, fire, liquid metal projections, blast, ...). Never try to imitate what this person is doing.
Two important points:
The thing about #2 that's easy to forget is that if a point has a voltage and path to ground, then it's possible for you to complete the circuit through your body and feet to ground (or through your desk, chair, etc...) - and this also works for some other common point, not only ground.
The secondary side of the transformer he's playing with is isolated from everything else, it's actually visible in its entirety in the video - it's the large white cable the Mehdi is wrangling into position. It is possible to touch one end of that cable without completing any circuit. However if you were to touch both ends of that cable (e.g: one hand on each end), then you become part of the circut. Depending on the voltage and your wetness, that could very well be incredibly dangerous.
Given that he has one or two turns on the secondary (depending on when in the video you're referencing) and many turns on the primary, indicates that the voltages involved here will likely not be very high... Voltage goes down, current goes up.
The subtle and important distinction is that Mehdi is not becoming part of the circuit, as he's only in contact with one point - his left hand, which is holding the spoon's bowl.
In addition to this, the voltage gradient extends around the wire, and down part of the spoon's handle, but not down the rest of the handle to the bowl. This is actually demonstrated quite nicely - the glowing hot bit is passing current, while the rest of the handle and bowl are not
Metal conducts heat fairly well, so the rest of the handle and bowl will eventually warm up... but he seems quite comfortable with the temperature in the video, which suggests the bowl (where he's holding it) is likely less than about 50-60°C.
I don't think it needs to be said... I hope it doesn't need to be said... Mehdi knows very well what he's doing, but a lot of his videos can be incredibly dangerous for anyone who has less in-dpeth understanding.
DO NOT DO WHAT HE DID.
The voltage is either low or he isn't completing the circuit. You can stand on a transmission line running thousands of volts. It doesn't matter how many amps (as long as you aren't heating the device to destruction or creating over temp) as long as the voltage isn't high, you won't have an issue, you can have a 9V system that does hundreds of amps (need a thick cable) but the voltage would have no more have an effect on you than a 9V battery because humans are at least a few k's of resistance (dry humans).
That person is a skilled circus performer who knows what he does. He was able to watch and publish his video afterwards because
He could resist the temptation to connect the transformer to the mains AC without removing the high voltage winding. The output of the full condition transformer would be enough for electric chair.
He is vigilant enough to avoid touching the mains AC wires. He touched the ends of his new secondary winding even when the mains AC input was ON, but the 1...2 volt output from his new secondary winding cannot cause noticeable currents through a human body, which has resistance tens of kilo-ohms. But it can melt milliohm resistance metal items, as we saw.
He surely tested that his winding detaching job didn't break the insulation. Such breakage could easily feed the mains AC to one's hands when he touches the iron core. The testing probably was clipped off.
I'm afraid there's numerous others who could easily do their last performance with the same equipment. Do not become one. As long as you do not have proper training and studies of electricity, stay away from making hobby circuits which are connected to the mains AC!
The reasons he wasn't shocked are the same reasons that you don't get shocked when you touch a plugged-in (good) phone charger:
When he took apart that transformer he was able to keep the primary coil intact, especially its insulation. That said, when things were melting it could have very easily damaged that insulating barrier and caused a primary-secondary short. He's kind of lucky that didn't happen.
Also, he didn't try energizing the transformer before he took it apart. Sadly, not everyone is wise enough to not do that: some use the secondaries of these transformers to make so-called ‘fractal art’ - and have electrocuted themselves in the process.
Remember Ohm's law, that says the voltage \$V\$ across something (also called a "potential difference") is equal to the current \$I\$ through that thing multiplied by the electrical resistance \$R\$ of that thing:
$$ V = I \times R $$
or
$$ I =\frac{V}{R} $$
The electrical resistance of a person is probably a thousand Ohms, or thereabout, from wet hand to wet hand, and if you have a voltage source of say 2V potential difference, holding one side of that source in each hand will result in the following current:
$$ I = \frac{2V}{1000\Omega} = 0.002A $$
You might feel a tingle with 2mA of current flowing through you, but that's all.
By contrast, if you connect a section of spoon between that source's terminals, then you can expect much, much more current. Let's say the total resistance \$R\$ of that wire and spoon combination is 0.01Ω (10mΩ), then the current would be:
$$ I = \frac{2V}{0.01\Omega} = 200A $$
This assumes that the voltage source is able to maintain 2V even while delivering that much current. The important thing is that there isn't a high enough voltage (potential) anywhere in the system to cause more than a couple of milliamps to flow through a person that comes into contact with any part of it, regardless of how much current is flowing in the wire and spoon. It's current that flows through the human body that is considered dangerous, not the current in the wire.
The only real danger posed by touching this low 2V system is getting burned by the rapidly heating elements in the circuit. The spoon here is dissipating (receiving) a lot of energy each second (power), which is being converted to heat.
With 2V across the spoon (actually slightly less, since the thick wire also has some resistance, and will "steal" some small fraction of the total voltage) and 200A flowing through it, to calculate power \$P\$ we find the product of those two quantities:
$$ P = I \times V = 200A \times 2V = 400W $$
That means 400J of energy is being dumped into the metal of the spoon each second, causing it to heat up. Within a couple of seconds that spoon will reach hundreds of °C, becoming a burn hazard, but not an electrical hazard.
There is another consideration, to do with the voltage of the electrical (mains) supply in the home. That supply provides a potential difference oscillating between +170V (US, Canada) (or +320V in Europe) and -170V (-320V). In other words, the potential difference between the live and neutral terminals of the wall sockets swap polarity 60 (US, canada) or 50 (Europe) times per second, the peak difference being 170V (320V).
The neutral side is tied to your home's earth node, (or the power-company's own earth, again depending on where you live). That means you and the floor you stand on have a very similar potential to the neutral node, and (as long as your electrician wired up the house correctly) you won't receive an electric shock from touching neutral. The potential difference between neutral and your home's structure is insufficient to cause significant current to flow should you come between them.
That's not the case for live. Touch that at your peril, because between your feet where you are in contact with the floor, and your hand where you touch live, is hundreds of volts. That will shock and possibly kill you.
So why, if Electroboom's system is being powered by mains electricity, don't you get a shock? If you look carefully, there is no direct connection between the wire/spoon and the mains supply. All 400W of that electrical power is being transferred magnetically, inside the transformer. Being isolated like this, the electrical resistance between mains live and the wire/spoon is near infinite, and again by Ohm's law, if you touched the spoon or wire, you can expect no current to flow between live and earth via your body.
