noondaywitch wrote:
The adapter may have an earth (ground) pin, but it isn't connected to anything in the magsafe.
That's not quite right. The ground pin is connected through metal rails in the AC cord connector to the metal nub on the adaptor; it's probably connected to the common. I don't have a multimeter to test, but it should be fairly easy to do so. (The two outer pins on the MagSafe connector are ground.)
But the point is that, connected or not, it doesn't make any difference, because the MagSafe adaptor is clearly designed to operate without earthing.
carl wolf wrote:
the "figure 8" cord is not grounded, and you're likely to get an electrical sensation when you touch the casework.
Then why doesn't everybody get "an electrical sensation" when using the "duckhead" AC plug
<http://support.apple.com/kb/HT2346>
which has no ground pin or earthing method?
The notion that one may get "an electrical sensation" because the mains outlet is not properly grounded or the adapter is not connected to the ground, etc, is grounded (ha!) in a failure to understand the design principles of switched mode power supplies (I suggest Sanjaya Maniktala's "Switching Power Supplies A to Z"). The "electrical sensation" is static electricity. Anything else means the adapter is malfunctioning and needs to be replaced ASAP -- no amount of grounding or turning the plug by 180° can fix that.