Every time I plug my MagSafe 2 power supply into an power outlet, this Mac's aluminum body gives me a mild vibrating sensation and sometimes an electric shock. After searching for info about my problem on many forums, they believe there's some problem with my grounding.
My country's electricity is about 220v. If I plug it into a 110v power outlet should it solve the problem?
I'm not an electrician so I don't really know what to do.
I've had this problem with a 2005 Powerbook, 2008 Macbook Pro, and 2010 Macbook Pro. Every Mac I've owned, in other words.
Macbooks come with a selection of two plugs for the adapter. One of them is an ungrounded plug ("AC wall plug"). From tech specs, In the Box:
MagSafe 2 Power Adapter, AC wall plug, and power cord
This, coupled with the metal enclosure, means you get a tingling sensation. You provide the earthing.
Use the grounded power cord instead, even if it's inconvenient.
This is known as "current leakage", and is usually caused by the device being grounded differently than your body is. Or the device being grounded differently than the metal desk, and your hand is the conductor between the device and the desk. See the Wikipedia entry for ground loop.
The voltage differential between the two grounding levels causes a little current to flow from one to the other. It's usually not a safety issue, but it is an annoyance.
This is basically the same thing as the "60 cycle hum" or "ground loop hum" you get on A/V equipment if one of your devices is grounded differently than another, and you're using an analog audio connection between them; the difference in ground levels causes current to flow from one box to the other over the analog audio connection, which sounds like a buzz at 60Hz, because 60Hz is the frequency at which Alternating Current alternates. (It may be 50Hz in your country.)
In some countries (US and possibly others), the AC connector that connects directly to your MacBook Pro's power brick is ungrounded, but the AC power cord is grounded. If you're using an ungrounded connection, switch to a grounded connection. Or vice-versa. See if it makes a difference. If trying out a grounded connection, make sure you have a proper working ground on the outlet you're connecting your power adapter to.
You basically want your MBP and everything else you or it could make a circuit with to be grounded the same way. If you have a metal desk that isn't grounded, consider getting a grounding cord for it as well.
Looking up resources for resolving ground loop problems in audio equipment may give you additional tips and suggestions for how to resolve this.
If that doesn't solve it, call Apple tech support and find out what your options are.
Your computer does not appear to be properly grounded when connected to the AC adapter.
I've worked with a Dell laptop that was supplied with an ungrounded AC adapter, and I was able to read up to 60 volts AC, at the 60 Hz mains frequency (though with low amperage), with my multimeter when one test probe was connected to the computer's case and the other probe was held with multiple fingers and connected to a grounded object. My personal HP laptop came with a grounded AC adapter and never had this issue. The laptop itself is unlikely to explain this problem, as the display is LED-backlit and does not need a high-voltage inverter to drive the backlight.
Most modern laptop AC adapters, including yours, accept both 110V and 220V input, but if the problem is not a site wiring fault such as improper grounding of your building's electrical system, using a socket in a different building, let alone a socket with different voltage output, will not make a difference as your AC adapter is at fault, not the wiring in your building. (Many surge suppressors and UPS units from manufacturers such as APC and Tripp Lite can detect improper grounding or other electrical problems in your building.) If this is the case, have your computer serviced as this can become very dangerous if the problem worsens.
In the unlikely event there is a site wiring fault, have an electrician correct the problem or notify a person managing the building about this problem. If possible, try to work elsewhere until the problem is resolved.
Your case is essentially the same problem as Dell Inspiron 15R gives electric shocks, so I am voting to close.
Is it about being barefoot and becoming a conductor for the electricity?
I had one bare foot on the floor while I was using my MBP and that is when I felt this electricity but when my foot wasnt on the floor, there was no current feel. because I wasnt the conductor for the electricity anymore.
There is actually a completely different possible answer to this.
Aluminum, which is what the case of most modern Macs are made of, is not particularly a good conductor of electricity. So the "shocks" you are feeling doubtfully have anything to do with the power supply, or even the power of your laptop.
Rather it's more more like due to the fact that aluminum is a very good conductor of radio frequencies due to what is known as skin effect wherein electricity, modualted at a high frequency, is conducted along the skin of an aluminum surface. What you are feeling then is most likely the effect of electricity/radio-frequencies e.g. your router, a local cell phone tower, etc. being inducted by the case of your computer and "finding ground" through your skin.
Of course electricity is never anything to take lightly, so if what you are feeling is an odd "tingly" sensation when you touch the case of your computer it's most likely due to the above. However if you are getting "shocks" which hurt you then you should bring it in for a checkout/repair immediately.
