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Unsure if I'm stating the question correctly, but I know there are warnings against quickly unplugging projectors suddenly because of the damage it can cause to the projector bulb. Is this applicable as well to laptop and desktop power cords assuming that the unplugging is done after powering off the computer?

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possible duplicate of laptop: Should one plug the AC first or to the laptop first. And, to restate what I said as a comment in that question: It makes no difference. The AC/DC transformation is a one-way deal, so it literally doesn't matter (both circuits are electrically isolated from eachother - or at least they should be!). –  Breakthrough May 9 '12 at 3:47
    
I don't think this is the same. I also think it does matter. You should connect the cord to the unit first, then plug it in to the outlet. Plugging a live cord into the unit is risky, although admittedly there's not much chance of a problem. But there's a right way and a wrong way to do everything, regardless of how much or how little risk there is of doing it wrong. Anyway, I don't see what difference the AC/DC transformation makes; you can shock yourself or cause a short circuit with either one, I know from experience during my electronic repair days long ago. –  Marty Fried May 9 '12 at 4:04
    
@MartyFried are you seriously telling me there's a difference between the action of "connect the cord to the unit first" versus "plugging a live cord into the unit"? Unless you're using a cable with exposed conductors (in which case, you shouldn't be using it at all), there's no difference. Yes, there's a difference between shutting the device off (in which case, graceful termination is always best), but when you're plugging it in, no, there's no difference. –  Breakthrough May 9 '12 at 4:13
    
@MartyFried define right way and wrong way, its a matter of opinion for everyone what is right or wrong. I suppose if you cannot pay attention you should not use electrical devices, or drive a car for that matter, that's my opinion. –  Moab May 9 '12 at 15:11

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For any device, it is certainly best to power it down before removing power, as you stated. But once this is done, it really doesn't matter how quickly you remove the plug, only that you pull it straight out to avoid bending the prongs.

When you remove the plug, there is going to be a point where the connection is broken. No matter how slowly you remove the plug, when it hits that point, there is no more power, unless you have a high enough voltage to arc across the air gap.

As for projector bulbs, they might benefit from a gradual reduction in power, but you won't get that from removing the plug slowly; you get that from some special circuitry that can vary the power on power down or power up.

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With the projector, the "don't unplug it suddenly" warning tends to be more due to needing to run a correct power down cycle to cool the stupidly hot bulb to a safe temp from memory. If deprived of power, you get a very hot bulb and no active cooling - which could fry/melt/make bad whatever is near the blub (particularly if you put it back in the carrying case) –  tanantish May 9 '12 at 13:40

There are no such issues with typical laptop or desktop computers.

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Care to explain why? –  Ivo Flipse Jul 15 '12 at 11:25
    
It's basically just because these are smart power supplies, not dumb things like light bulbs. They have circuitry that controls the flow of power to their sensitive components. –  David Schwartz Jul 15 '12 at 18:02
    
True, light bulbs are flimsy and have no smart circuitry. But the thing you have to remember is that human error can trump smart power supplies and cause issues. –  Christopher Chipps Oct 9 '12 at 22:47

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