Preparing to hook up an LED, I discovered that it lights up, when I touch one lead with the other connected to my bench power supply. Why is it so?
I am no electrical engineer, I am a computer scientist who's interested in electronics. These potential differences and "uncommon" paths of electricity always fascinate me. At this point I have no explanation for this phenomenon other than "there has to be an unusual path of electricity through my body".
If you can explain what is going on please leave a comment below and enlighten me and anyone who is wondering what's going on too. Or is there something fishy going on in the wiring of my apartment?
Here are some additional measurements I made after recording the video.
| Multimeter probe A | Multimeter probe B | AC V |
|---|---|---|
| Positive PSU out | Floating | 1 V |
| Positive PSU out | My Hand, sitting, feet off floor | 3.8 V |
| Positive PSU out | My Hand, sitting, feet on wooden floor | 6.7 V |
| Positive PSU out | My Hand, sitting, feet off floor, other hand on ground connection | 0.45 V |
| Positive PSU out | My Hand, sitting, feet on wooden floor, other hand on ground connection | 0.9 V |
| Positive PSU out | Ground connection | 0.35 V |
| Positive PSU out | Ground connection, Negative of PSU grounded | 0 V AC / 5 V DC |
These measurements were taken with the power supply set to 5 V / 20 mA output (DC), but the values seem to be independent of the set voltage of the PSU (except the last measurement).
Looking at these voltages it is unsurprising that the LED light up when I touched it with my hand not on the ground connection. But why are there up to 6.7 V between the PSU and the floor? Is this normal and I am just making a fuss for nothing or is there something interesting to be found here?
Please do let me know what you think in the comments. :)
