[media]http://youtube.com/watch?v=XDf2nhfxVzg[/media]
This guy is fucking awesome.
The main reason for divorce is marr-iage
I love him
He didn't really explain one of the most confusing situations here: very high-voltage, but low-current (i.e. from transformers).
The eyebrow wiggle at the end was great.
danger danger, high voltage!
[QUOTE=JgcxCub;44196545]He didn't really explain one of the most confusing situations here: very high-voltage, but low-current (i.e. from transformers).[/QUOTE]
Such systems are built with extremely high resistances, which is why the current that runs through them is low. I don't think I understand what you're asking.
[QUOTE=JgcxCub;44196545]He didn't really explain one of the most confusing situations here: very high-voltage, but low-current (i.e. from transformers).[/QUOTE]
There are plenty of transformers that'll kill you with a high voltage. Like these:
[IMG]http://i.imgur.com/arG7mfj.jpg[/IMG]
There's a saying... hahah
[editline]11th March 2014[/editline]
And for those of you who haven't seen strobe lights and water, enjoy.
[media]http://www.youtube.com/watch?v=TH1mJpOnxDE[/media]
Alright I made a couple flowcharts to show my thought process when working on live circuits:
[IMG]http://i.imgur.com/nX3pFek.gif[/IMG] [IMG]http://i.imgur.com/4ilGhyg.gif[/IMG]
You always need to take into consideration voltage, then current. It's never just one or the other.
[QUOTE=JgcxCub;44196545]He didn't really explain one of the most confusing situations here: very high-voltage, but low-current (i.e. from transformers).[/QUOTE]
He referenced the equation that answers your question in the video: V = IR
Across your tongue, lets say there's 100 Ohms of resistance. There's more, but that's just say there is 100 Ohms
If you have a 10V supply which can supply infinite current (in the video, his can supply up to 150 Amps) then:
10 = I*100
=> I = 10/100 = 0.1A
That's 100mA across your tongue but there isn't enough voltage to produce a current through the rest of your body, because it has a much higher resistance than your tongue.
Something like 10mA of current through your heart is enough to kill you. Therefore, if you touch a 40kV power supply, and it can supply say a modest 1A, and lets say the human body has a resistance of 500,000 Ohms:
V=IR
40,000 = I*500,000 (I is still unknown because our power supply can PROVIDE 1A, but that doesn't mean the load (I.E the body in this case) will draw the full 1A)
I = 0.4A = 400mA
So that scenario above would likely kill you
disclaimer: use this info at your own risk, parts of it may be factually incorrect. i accept no liability for any harm caused. please don't stick your tongue into a mains socket or something
This guy is brilliant. That fucking ending.
[QUOTE=Abrown516;44199626]Such systems are built with extremely high resistances, which is why the current that runs through them is low. I don't think I understand what you're asking.[/QUOTE]
No, even in a low resistance circuit. A high turn-ratio transformer will output a very low current despite both a high voltage and low resistance. I believe it's [I]impedance[/I] (or rather, reactive effects) rather than resistance, but i've never quite got a good enough explanation.
[QUOTE=JgcxCub;44201620]No, even in a low resistance circuit. A high turn-ratio transformer will output a very low current despite both a high voltage and low resistance. I believe it's [I]impedance[/I] (or rather, reactive effects) rather than resistance, but i've never quite got a good enough explanation.[/QUOTE]
Conservation of power. A transformer of say a 1:100 ratio will multiply the primary voltage by 100 times and to conserve power, it divides the primary current by 100 times.
So if you put 1A @ 10V in you get 10mA @ 1000V out.
And to verify...P=IV so
Primary: 1A * 10V = 10W
Secondary: 10mA * 1000V = 10W
Its a trade off really. You have to give up current for lots of voltage or give up voltage for lots of current.
[QUOTE=No_Excuses;44201727]Conservation of power. A transformer of say a 1:100 ratio will multiply the primary voltage by 100 times and to conserve power, it divides the primary current by 100 times.
So if you put 1A @ 10V in you get 10mA @ 1000V out.
And to verify...P=IV so
Primary: 1A * 10V = 10W
Secondary: 10mA * 1000V = 10W
Its a trade off really. You have to give up current for lots of voltage or give up voltage for lots of current.[/QUOTE]
I know it's conservation of power. But what is the actual physical process, or manifestation, that reduces the current? I assume it's reactance of the transformer coil, but i've never been quite sure.
[QUOTE=JgcxCub;44202788]I know it's conservation of power. But what is the actual physical process, or manifestation, that reduces the current? I assume it's reactance of the transformer coil, but i've never been quite sure.[/QUOTE]
Transformers have low resistance. They just manipulate voltage
[QUOTE=Code3Response;44203388]Transformers have low resistance. They just manipulate voltage[/QUOTE]
That doesn't answer my question.
[QUOTE=No_Excuses;44199808]Potentially not lethal[/QUOTE]
Oh that's reassuring.
[QUOTE=JgcxCub;44203424]That doesn't answer my question.[/QUOTE]
I learned it ten years ago in school, but isn't a transformer using two coils (with different amounts of windings) and one of them generates a magnet field and the other one creates electricity from it again? I guess the best comparison is to a big and a small gear. The energy coming out of the gearbox is the same, but the RPM aren't.
I still love when he tries the tongue and glares at the machine for lying.
[QUOTE=Mingebox;44203564]Oh that's reassuring.[/QUOTE]
The problem is theres so many variables to consider. If you're soaking wet standing in a puddle of water, it won't take much to kill you. On the other hand if you have really dry skin you have a higher tolerance.
Basically you shouldn't work on live circuits is what I'm getting at.
[QUOTE=Robber;44203738]I learned it ten years ago in school, but isn't a transformer using two coils (with different amounts of windings) and one of them generates a magnet field and the other one creates electricity from it again? I guess the best comparison is to a big and a small gear. The energy coming out of the gearbox is the same, but the RPM aren't.[/QUOTE]
Doesn't answer my questionnnnnnnnnn
[QUOTE=JgcxCub;44202788]I know it's conservation of power. But what is the actual physical process, or manifestation, that reduces the current? I assume it's reactance of the transformer coil, but i've never been quite sure.[/QUOTE]
I think what you're asking has to do with the physics of transformers. Magnetic flux, Faraday and Lenz's law, etc. It can be explained but you may need to do research on the topic.
But looking at some other posts, keep in mind...the secondary still follows ohms law. Say we have our 1:100 transformer... If you put a 10ohm load on a secondary producing 1000V, it will try to supply 100A (10,000A at primary). A very large transformer will do this fine. Like one the size of a shed.
A small one (mot) won't because of resistances in the primary and secondary would cause catastrophic heat dissipation, as well as the fact that the core would saturate with flux long before currents that high.
Oh man, this guy is golden.
Related, more crazy:
[media]http://www.youtube.com/watch?v=ut5DXxK1dvk#t=719[/media]
reading about electricity always freaks me out for some reason
[QUOTE=No_Excuses;44212111]I think what you're asking has to do with the physics of transformers. Magnetic flux, Faraday and Lenz's law, etc. It can be explained but you may need to do research on the topic.
But looking at some other posts, keep in mind...the secondary still follows ohms law. Say we have our 1:100 transformer... If you put a 10ohm load on a secondary producing 1000V, it will try to supply 100A (10,000A at primary). A very large transformer will do this fine. Like one the size of a shed.
A small one (mot) won't because of resistances in the primary and secondary would cause catastrophic heat dissipation, as well as the fact that the core would saturate with flux long before currents that high.[/QUOTE]
The funny thing is, I'm a second year physics student at university, and I've still never received a more definitive answer other than "impedance".
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