Ever since I got a phone with a metal chassis I get this issue : if my phone is plugged to a train electric outlet and I simultaneously touch my phone and any metallic part of the train (such as an ventilation grid) I get a small, but painful jolt.
Now, as I understand it, insulation between the phone chassis and the train should be provided by
- the train electric supply system
- the charger's transformer
- the separation between the phone's battery and chassis
So why do I get those shocks ?