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How come EMP doesn't affect humans (or does it?)

by MowJo
Tags: affect, humans
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Nov14-12, 05:28 PM
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I mean EMP from a nuclear device (HEMP, which crates fast consecutive pulses).

It electrocutes electronic devices, regardless ON/OFF or even when disconnected from the grid. So why it will not electrocute humans? Humans are conductive, they can close a circut, no?

For example, if humans insert fingers to outlet they will receive an electric current.

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Nov14-12, 06:40 PM
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Only new-model humans built with transistors are affected by EMP. Older humans who are built with vacuum tubes (such as the new Soviet Man) would be unaffected.
Nov14-12, 07:30 PM
P: 5
My understanding in physics is not great but I'm serious about this subject.
Look this is an answer from another place in the internet:

"An EMP will cause a surge in current in any electrical circuit. Usually, it's more than the circuit can handle, and it burns out. The human nervous system does use electrical impulses, but it doesn't operate in the same sense as a computer does. It's a common misunderstanding, seeing as nerves are often portrayed as wires.

Instead of carrying current like a wire, nerves operate more like a row of falling dominoes. Along the length of the nerve, there's an artificial imbalance of ions (sodium and potassium) that's kept out of balance by tiny pumps within the nerve. This imbalance in ions results in an imbalance in charge, which means there is a voltage difference between the inside and the outside of the nerve. Once the nerve fires, tiny channels in the surface open up, the ions rush through, and the charge flips. This flip causes the next channels down the line to open, and so on and so forth, and the signal is carried down the length of the nerve. Once it reaches the end, it causes the neuron to release chemicals that conduct the signal to the next neuron down the line.

Since neurons carry their signals chemically, rather than via current, (and nerves aren't set up like electrical circuits) an EMP wouldn't have any effect. BUT, since electrical charge is involved in conducting the signals, the nervous system is susceptible to electric shocks. The same is true of muscles, which, electrically, are very similar to nerves. A shock can trigger the ion channels on the surface of the cells to open up, making the nerve fire (or the muscle contract)."

This is a long and nice answer but it doesn't really answer. Because there is an immediate question: What's the difference between an EMP and an electric shock?
Why EMP can't trigger the ion channels in our nerves?

This is an open American government document to the US congress:

On page 9 (near the bottom) it says " A nuclear explosion produces gamma rays, which interact with air molecules in a process called the Compton effect. Electrons are scattered at high energies, which ionizes the atmosphere, generating a powerful electrical field. This EMP effect is strongest at altitudes above 30,000m, and lasts so briefly that current cannot start flowing through a human body
to cause harm to people."

OK, so it means that, with enough time, an EMP can cause a flow of current through a human body?

Nov14-12, 07:48 PM
P: 139
How come EMP doesn't affect humans (or does it?)

Source for MowJo's first quote since one should generally credit the original author.
Nov15-12, 06:18 AM
P: 5
Yeah, I'm sorry about that. I was afraid that putting that specific link will break a rule or something.
Nov15-12, 09:47 AM
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Electronic circuits have good conductors. While humans are not perfect isolators, our internal resistance is significant.

An electric shock by touching the power grid is longer, and you have a direct contact to good conductors.
Nov15-12, 11:22 AM
P: 5
So, mfb, you think that if the EMP is strong enough and lasts long enough, it will affect humans?
Nov15-12, 12:03 PM
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If something is strong and long-lasting enough, it will affect humans, that is true for nearly everything.
EMPs deposit some fraction of their energy in material. Increase the intensity enough and at some point you can evaporate anything within some range.
Nov15-12, 01:53 PM
P: 5
So, theoretically, how long a maximal EMP (I think about 50 kVm) from a HEMP device should last to electrocute a grown-up human being?
Nov15-12, 02:29 PM
P: 87
I do not think a wider pulse will cause extra damage. It is the large change in field strength in a very short time that causes the large induction currents.

You would have to increase the maximum to make the rise and fall of the pulse to last longer whilst maintaining the graidient, to increase the damage.
Nov15-12, 09:59 PM
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Human flesh is actually rather conductive, and it's the main reason EMP pulse has little effect on our nervous system. It's pretty-well shielded. If you look at penetration depth of various EM frequencies, you'll notice that it drops off dramatically in microwave ranges.

An EMP pulse can be seen as a very short burst across a very broad spectrum of frequencies. A lot of the EMP power is in higher frequencies, which simply do not penetrate human flesh.

The fact that powerful EM radiation can effect humans is demonstrated by the Active Denial System, which super-heats a very thin layer of epidermis, causing sensation of burning. Note that while it easily penetrates clothing, it does not penetrate deep into person's tissue, causing heating only in the skin of the target.

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