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VenuS

I get electro shocked by my motherboard.

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If you stuck an ammeter (the DMM measuring current) across the poles of a 120V AC line in you house, you've created a direct short. As a result, there is infinitely small resistance and infinitely large current will want to flow. Ohm's law, simple relationship. I = V / R, where I is current (engineering standard symbol), V is voltage, and R is resistance. The internal resistance of your DMM on current setting is somewhere in the range of maybe 2 ohms, and the wires in the house maybe half an ohm, depending on their length. Therefore, to approximate, you have I = V/R = 120/2.5 = 48Amps. However, you'd likely burn the 10A fuse in most DMMs first, or pop the home fuse/circuit breaker. If neither of the above happen, you'd likely start a fire cause the wires in the wall and especially the wires in your DMM will heat up due to carrying so much current.

I have no idea where you measured 11mA but if that's the case, how do you power your computer? If it has a 600W power supply, then it's probably running at an average of 500W or so, depending on your hardware. Power is equalled to current times voltage. So you have a maximum input of 120v*.011A = 1.32W. Definitely not enough to power a computer that consumes 500W. Accounting for inefficiency in the PSU, the wall plug is probably supplying about 4.5A for your computer at 500W. Go figure.

Hope everyone enjoys a simple lesson in electricity.

 

J

 

 

Thanks for writing it down for the electricity "noobs"... ;-) ... I was just too lazy to do it that way...haha...

 

Good luck I'm an engineer in electrical power supplying...

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.02 Amps is the lethal dose, it doesnt really matter about the voltage. For example 120V AC coming out of the wall wont do much of anything to ya because it only carries .011A.

 

The voltage does matter though. V=IR, so in order for .02 amps to apss thru you, the voltage must be high enough to allow .02 amps to pass thru your body (which has a quite high resistance). See this link for more: http://www.dribin.org/dave/blog/archives/2.../amps_vs_volts/

 

Sorry for being so off topic...

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Next thing you know someone is dead on the news because they "heard on the internet" that the wall jacks only carry 0.011A, not enough to kill them, and they wanted to know what it felt like ... :rolleyes:

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Next thing you know someone is dead on the news because they "heard on the internet" that the wall jacks only carry 0.011A, not enough to kill them, and they wanted to know what it felt like ... :rolleyes:

Haha....yeah...so, I will say this for everyone again:

 

A voltage of 50V AC or above can be harmful for the human body by either hurting the heart, or poisoning your blood!

 

A voltage of 120V AC or above is very dangerous, and cause very serious injoury to your heart and/or blood!!

 

Whenever you don't know 100% exactly what you are doing, you should never repair or do anything else with dangerous high voltages (and 120V AC IS a dangerous high voltage!!)

 

OK, so, now I can sleep better...hehe

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Current, measured in amps is what kills, not the voltage.

 

Voltage must create a circuit for the current to follow through.

 

It takes very little amperage to kill &

the amount of voltage required to complete a circuit varies depending upon resistance.

 

The resistance of the human body can vary greatly.

Are you sweating? Less resistance & the lower the voltage required to complete the circuit.

 

The bottom line is DO NOT TOUCH ANY VOLTAGE SOURCE OVER 24/36 VOLTS!

 

:angel:

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Current, measured in amps is what kills, not the voltage.

 

Voltage must create a circuit for the current to follow through.

 

True enough. Most people aren't aware that the static shock you get after rubbing your socks on the carpet and then grabbing the doorknob can be tens of thousands of volts. Which is why static discharge can be lethal to your computer, even at tiny currents (which is what a static discharge is, huge voltage and tiny current). (That's for the noobs, not you david.)

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Can anyone explane how could that happen?I mean whats going inside the PSU that it spread electricity all over the board?

 

Might it be short circuit on the mobo its self?Even when i ground the PSU to the mobo/case it didn't helped.....

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^no, if you got zapped by AC, the mobo cannot just create AC, it has to get it from the PSU, so no, the PSU is your problem.

 

*EDIT* get an Antec, enermax, ocz, etc. power supply before you fry yourself or your components :)

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I forgot to tell that i was without shoes on the ground when i got that shocking.....

But in the same time i opened my other working PC and touched it same places and i didn't got any buzz...

 

ahhhhh....daring one aren't we?

 

Curiosity killed the cat! :cat:

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Were you grounded at the time? Have a ground-strap on? Even though you had the motherboard grounded on a wooden surface, the board itself has capacitors that store electricity. If somehow you might have made contact with the capacitor or a lead to the capacitor and then touched the RAM, the store of electrons in your body from the capacitors will discharge immediately.
Laying a PCB on a wooden table insulates it, it does NOT ground it.

 

As the leads from these caps come through the PCB very close to each other,

any discharge would only travel through about 1/10 if an inch of finger tip,

also none of these caps could be charged to over 12V as that is the highest voltage perovided to the mobo.

 

Dave :angel:

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