It's leakage current from the mains power adaptor
The tingle you are feeling is leakage current from the power adaptor (ie the "brick").
My MPB power adaptor came with two country-specific mains plugs (Australia, 240v) - the first is a neat 2-pin plug which clips directly onto the power supply. The second is a standard (Australian) 3-pin plug with approx 1 meter of mains cord attached.
The third pin provides the earth connection.
When you use the 2-pin plug: tingles
When you use the 3-pin plug: no tingles.
Pity that Mac didn't include an earth pin on the plug adaptor which clips directly to the supply.
The tingle you are feeling is leakage current from the power adaptor (ie the "brick").
My MPB power adaptor came with two country-specific mains plugs (Australia, 240v) - the first is a neat 2-pin plug which clips directly onto the power supply. The second is a standard (Australian) 3-pin plug with approx 1 meter of mains cord attached.
The third pin provides the earth connection.
When you use the 2-pin plug: tingles
When you use the 3-pin plug: no tingles.
Pity that Mac didn't include an earth pin on the plug adaptor which clips directly to the supply.