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I'm really confused if I should plug in the AC first , or the laptop side first.

I found lots of links on google , mostly personal habits , so I really want someone here to explain these knowledge to me.

I want to know both the order when powering on , and the order when power is off.

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closed as not a real question by Breakthrough, Sathya Apr 30 '12 at 18:20

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don't think its a problem doing it either way –  Megan Apr 30 '12 at 16:14
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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!). So long as it's an OEM adapter (i.e. certified to various legal requirements, including ISOLATING the secondary side from the primary), it makes no difference. Be careful using cheap, uncertified/fake 3rd-party adapters, although the risks posed by those chargers apply regardless of which order you plug them in. –  Breakthrough Apr 30 '12 at 16:24

3 Answers 3

As someone who has worked on systems for over a decade, I have yet to see a situation where either order matters. Even on really old laptops I've never seen or heard of issues regarding order of connectivity.

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I gotta go with this. I mean, regardless of the age of the laptop, who hasn't had to plug it in after using it on battery for a while, when they didn't want to lose what they were working on. That right there proves it doesn't matter what order you do it in. Older laptops, new laptops, universal power adapters, original adapters... none of that matters. –  Bon Gart Apr 30 '12 at 17:43

It must be safest to plug or unplug leads into the laptop when no power is present. This makes it potentially less harmful to the laptop if you somehow manage to misalign or short conductors when pushing the connector in. However, connectors are designed to prevent this sort of problem - so it should be rare unless you use an inordinate amount of force.

Turning on

  • plug power lead into laptop
  • plug power lead into electrical outlet
  • switch on at electrical outlet (if applicable in your locale)
  • switch on at laptop

Turning off

  • switch off laptop
  • switch off at outlet (if applicable)
  • remove plug from laptop
  • remove plug from outlet

In reality I expect unplugging is rarely a cause of any problems. You might theoretically draw a small spark from a live conductor which could cause problems.

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I should add that anybody handling such dangerous devices, like laptops and power adapters, should use plastic gloves as insulation at ALL times... –  TFM Nov 24 '12 at 11:50
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@TFM plastic gloves are not a replacement for a grounding/wrist strap. If the static charge builds up to a significant amount in your body, it's quite feasable for the spark to get across the thin amount of rubber. Furthermore, if you choose another type of glove (i.e. latex, vinyl), you might cause more static build-up than if you omitted the gloves to begin with (this depends on your environment and what materials are around you). –  Breakthrough Nov 24 '12 at 13:47
    
@Breakthrough: So latex is better? –  TFM Nov 24 '12 at 14:06
    
@TFM absolutely not; using a balloon as an analogy (which are made from either latex or rubber), I'm sure you know how easily you can make static build-up by rubbing it on your hair or another type of fabric. While I'm not arguing that it would necessarily make things worse (although it certainly can if you're not careful), I would argue that it's not a replacement for a grounding wrist strap, or even simply discharging the static from your body to ground. –  Breakthrough Nov 24 '12 at 14:14
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Rubber has less resistance than air, soo if it goes through the air it'll go through rubber. Also rubber can create static friction. I personally wear a faraday cage whenever I unplug any electronics, and try to remove any cats by whatever means necessary. Sometimes to prevent any static I'll run a humidor while misting my laptop with flourinert before plugging in. –  VoronoiPotato Nov 26 '12 at 13:50

Most circuits in modern laptops should be able to handle both situations.

However, looking at the situation, plugging into the laptop first and then plugging into the wall is no different than plugging any piece of eqt. in that doesn't have an adapter. The brick/adapter will handle the contact/make/break as the plug slides in.

In a poorly design system if you connect the adaptor after the fact, there will be contact make/break and the DC supply will bounce around. This causes false starts and resets.

But like I started out with, this shouldn't be an issue with modern designs because they are designed to handle it. Years ago it would have been an issue, perhaps that is why people still think it's important.

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