My cable to charge my iPad has recently exposed some metal wire (due to the plastic insulating splitting). How dangerous is such a wire? If I was to touch the wire when plugged in to the mains, what would be the likely outcome?
closed as off-topic by Voltage Spike, Enric Blanco, Nick Alexeev♦ May 5 '17 at 14:09
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As pictured, the outer insulation jacket has cracked or split (because of cheapness on apple's part which they refuse to acknowledge and recall, but I digress), exposing a metal braided wire. This wire is a shield cable, used to protect the signal carried by the wire from interference, and prevent it from interfering with other devices. That shield braided wire surrounds another, thinner piece of insulation, which has the actual power and data wires inside.
The shield is often tied to the ground return wire of the cable, on one or both ends, and typically is safe to touch. The typical metal cased computer would be grounded in the same way, and these can be freely touched without harm. As the iPad is a low voltage DC device, and that crack appears on the lightning connector end, you would not be exposed to mains voltage.
That said, the cable has been compromised, and continuing to use it as such is up to you. You should insulate the crack by some means, heat shrink tubing, electrical tape, plastic molding, etc, not just to prevent accidents, but to strengthen the cable at that point to prevent further damage. It is now a weak spot for the inner wires, a stress point where bending will have a greater impact.
It can be lethal if you are not using an properly isolating charger, Ken Shirriff explains why in this detailed blog posting. In a standards-compliant charger, there are various design aspects which ensure your safety, which include using recognised safety components, materials and spacings between live parts and connections which lead to the device.
If you are using the correct charger, there should be no effect from touching any of the connection points on the USB side, but when it comes to safety, extra layers of protection are always a good idea, so get a new lead as soon as you can.
If you touch it, it will be harmless. It may however cause damage to your charger or to your iPad if you short circuit it or if you touch it to a grounded conductor.
Are you referring to the braided shield overlay or the positive or negative wire. The shield is just for interference and is connected to the return on one end. The positive is 5vdc, current in the range of milliamperes, not sure how much, and the negative is the return, so no real danger there unless shorted.
Mechanically compromised cables are dangerous because:
1) There is a small risk of fire, the cables could short out and heat up thus causing a fire.
2) It could compromise the device (brownouts are never good, especially if they are momentary.
So proceed at your own risk.
There probably isn't that much risk for electrocution, because most laptop adapters are lower than 20V.