Interior wall: Problem with wiring and no ceiling joist to fasten to

[KJD]

noob question: need to temporarily put up an interior wall during renovation, but I'm a bit unsure about the electrical wiring... I've found two studs in a gable outer wall, which I plan to attach a vertical stud to, but I got an indication of electrical presence with a construction scanner (ps-38). The indication isn't clear, and there's a similar issue on the other wall (behind me from the viewpoint of the photo).
Can I trust that electrical boxes are attached to the side of a wall stud and that the electricity is run straight up along the side of that stud? I don't have a voltage meter available at the moment.
Additionally, the space is open up to the ridge here (staircase), and I'll likely need to build temporary ceiling joists as well to make a stable wall.

There's another option without electricity and with a stud in the ceiling! But then the family won't have a corner in the hallway to sit and put on outdoor clothes and "land" in the hallway... I'll get in trouble later instead.

Comments? Is the question understandable?

 

[nikasp]

You don't need to screw at all, so you avoid that problem: https://www.byggahus.se/forum/threads/innervaegg-utan-att-skruva-i-golv.285805/

 

[KJD]

Ok, interesting. This is above a staircase, so I feel the wall must be very stable + I don't have a ceiling joist, as it's open at the peak. I opened the wall on one side to see how the wiring was installed, and it was mounted from a junction box and in the middle of the joist side. Then I bought a stud detector from Stanley and got an indication that there's wiring trouble on the other side of the joist as well . What do you do in this situation? If you turn off the power, can you trust driving in a wood screw and that it goes in correctly, or is that foolish? I don't want to change now, as I've nailed the floor joist to the parquet . (note that this is a temporary wall, during the renovation of the basement).
Tips welcome!

 

[KJD]

Finally gave in. Moved the wall and attached studs only to the chipboard. It became impressively stable. Fastened securely for more sturdiness. Nice not to have to think about the electricity .