Why doesn't a stripped/cracked MagSafe power cable shock? Behold, the fate of all (poorly handled) MagSafe power cables:


Why doesn't this shock me?  I've read that MagSafe cables are low voltage, but I don't even get a tingle.  Is there any danger of shock, arcing, and/or fire from a MagSafe cable in this condition?  If so, is a strip of electrical tape over the exposed wire a sufficient 'fix'? 

Bonus question: what is the source of the green and yellow discoloration?
Magsafe cables only carry voltages ranging from 14.5 to 20 volts, which is not nearly enough to be able to feel. For more information, see this Electrical Engineering Stack Exchange question. You would not be able to touch the actual conductors anyways as the metal "wire" that is visible in this picture does not carry any current, as it is just shielding around smaller insulated wires. It is unlikely for arcing to occur, but you should still get the charger replaced soon. Like iPhone and iPad chargers, always buy MagSafe chargers from an Apple Store or the Apple website as ones bought on eBay and Amazon are known to be non-UL listed counterfeits.