Vibrate when touching an anodized surface! Depending on grounding?

I have had a very strange experience.

My notebook has an anodized aluminum surface.

When I stroke it with my finger, I notice a kind of vibration in my finger. Similar to the stick-slip effect.

So far so good.

Now I pull out the power plug, or touch the surface with the other hand, the vibrating disappears.

Since the power supply does not have a protective conductor, a very low leakage current can occur or there may be some voltage on the notebook.

Since the anodized layer but insulating acts I'm here with my knowledge in the end.

Has anyone ever noticed something similar and an explanation for it?

The anodized layer is made of alumina. Although this is insulating, but also has a relatively high https://de.wikipedia.org/...vit%C3%A4t of 9. This means that if the layer thickness is 5 microns, then one has a capacity of about 1.5 uF per cm ^ 2. This is theoretically sufficient to allow a current of over 100mA to flow. In your case, it was probably less than 1mA.

How insulating the anodized coating works, I would not be sure… Power supplies without protective conductor have the property that about 110V AC voltage is applied. They can e.g. Also lead to the fact that switched off LED strips light up.

The 110V are safe and can only be measured with an oscilloscope or sensitive measuring device. As soon as a bit of electricity flows, it is much less. But it is enough to feel this feeling.

Each AC voltage can be inductively transferred to housing parts when there's no ground or e.g. The voltage regulation is not sufficiently shielded. Most of the time, this "effect" occurs in 230V household appliances such as a refrigerator or toaster when the protective conductor is disconnected.

Due to the extra-low voltage of the external power supply, this is not dangerous for the notebook, but m.E. Nevertheless a serious defect, which should be complained.

Thanks, that's a logical explanation. The vibration seems to be synonymous with 50Hz. If you shed an additional layer, then it will even be audible