Shock can also be via the casing of the Macbook. I may have one of these dodgy plugs from a 2011 11" MBA that I started using as a spare so to preserve my most

Shock can also be via the casing of the Macbook. I may have one of these dodgy plugs from a 2011 11" MBA that I started using as a spare so to preserve my most recent replacement. (third or fourth bent/broken cord) When you place either hand on the MBA casing beside the trackpad you get what feels like a buzzing in your lower palm. If you are shirtless (common on these balmy summer nights) and touch your stomach against the edge you get a definite kick like you burnt yourself.