This question already has an answer here:
Most outlets in my house are non-grounded (line and neutral contacts only). I just bought a Hakko fx-888d soldering station, and immediately noticed that touching the iron-station cable gives the same sensation as when I plug in my aluminium Macbook. This sensation disappears when I unplug both devices. I measured the voltage between the ground (from a grounded outlet in the bathroom) and the Hakko cable; it was about 100...110 V (I used the AC regime of the multimeter).
What causes this voltage? Is it dangerous for me or for electronics?
UPDATE: I live in the Netherlands, where having 2 contact outlet is allowed. The human safety is ensured by RCD = GFCI. The house is not that old and is well wired (with copper) and grounded, where required. While I'd be happy to improve it and rewire the ungrounded outlets, it doesn't make much sense as I am renting.
Also, plug orientation here is arbitrary (plug can be inserted in the outlet in two ways), so the design never relies on which wire is neutral and which one is line.