Chacham check up on boneh that is not attached to the ground. I’m pretty sure that you will find it to be a machlokos, if my memory serves me correctly.
Even if we don’t pasken like the shitah that holds that boneh is only when attached to the ground, this will probably be considered a sfek sfekah. Machlokes about boneh, and machlokes if completing a circuit is considered boneh at all, or if it is assur for a different reason.
BTW once we are on the topic of electricity, i think that you will find a tshuvah in the end of Achiezer (Rav Chaim Ozer) that strongly implies that the issur is mederabanan.