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EMP effects?

  1. Nov 12, 2009 #1
    In a recently released computer game there is a scene where a nuclear bomb goes off in space over the active war zone on the east USA coast (too high for anything but EMP). Moments later, it starts raining helicopters and everything that uses electricity, from lights to laser sights goes out. Curiously, diesel generators appear to keep working, continuing to power the supposedly-burned out lights in one place.

    In another media thing, a TV series, when a nuke is about to go off all the computers are turned off "to prevent them from being damaged by EMP".

    How much sense is there in these scenes? Will some class of modern helicopters be brought down by EMP alone? Does being on/off matter for a laptop against EMP? What devices should be un/affected by it?

    And, second question - human brain and body is pretty much an electronic device of a distinct design, how is that it is completely unaffected by EMP (or is it?)?
  2. jcsd
  3. Nov 12, 2009 #2
    I'm not sure about helicopters but laptops would die on or off and the reason humans are unaffected is because we are (largely) not magnetic. There are pretty much no electronic devices (unless specifically shielded) that will not be effected I would think.
  4. Nov 12, 2009 #3


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    Yes unsheilded electronics are vulnerable to EMP.
    It wouldn't necessarily rain helicopters they do flutter down relatively safely when their engines fail.
    And it is more difficult to produce an EMP burst than some Bond movies suggest!

    You are pretty well shielded inside a bag of salt water, also your wires aren't very long.
    The amount of voltage generated depends on the field and the length of the wire, a very long wire gets a large voltage generated even if the filed strength (volts/m) is low - that's why cross country powerlines are vulnerable to solar storms.
  5. Nov 12, 2009 #4
    I would need to do a bit of digging to be sure of this... I read somewhere that the old vacuum tube devices are not particularly susceptible to emp nor were old (real metal ) non electronic cars. This might be simply a matter of overbuilding. Today's electronics cannot handle the voltage/ amperage spikes. Hmmm. Along the length of wire thought... taking the US as a single device, there are a few more magnitudes of wire plugged into the grid at any given time than ever; the devices are somewhat more fragile then ever too.

    As for them being on or off it is mostly a moot point. It is the relative movement of a wire and a magnetic field that causes the effect; being "off" just a way of saying that the device is not getting power from the grid and in most modern devices it doesn't even mean that; they're always on just in some lesser capacity. About the only way to protect your stuff is a Faraday cage.

    It is interesting that the US has not taken(that I'm aware of ) any steps to avoid the problem of simply shorting out the grid as we did to the Iraqis, nor the aforementioned emp.
  6. Nov 12, 2009 #5
    Yup, solid-state electronics is much more vulnerable to EMP than vacuum tubes.

    It's safer to turn the computer off, even a weak EMP can corrupt your operating memory and mess up any running programs. And the level of EMP needed to cause damage would be lower if the system is powered on (EMP-induced voltages would add to operating voltages). But a stratospheric burst would be powerful enough to fry any unshielded computer, whether it's on or off.

    Humans are more chemical than electronic. Neural signal transmission speeds are measured in tens of meters per second. The only thing that lets our brain function at a reasonable speed is the immense level of parallelism.
  7. Nov 13, 2009 #6
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