175Views2Replies

Author Options:

How is it that I can measure voltage across an unplugged wall wart? Answered


I have a 9V wall wart that's been unplugged for 2 days.  I hooked it up to my volt meter with intentions of checking the polarity as I plug it in.  Without plugging in the wall wart I attached the meter leads to the exposed wire of the wall wart.  It immediately showed a voltage of -10 point something.  I was glad to find the wires were backwards which explains my fried regulator; however how is it that I was able to pick up a voltage, even after discharging it the voltage slowly rose again, unplugged!  Does this have anything to do with earths magnetic effects on the inductor?

Discussions

The forums are retiring in 2021 and are now closed for new topics and comments.
0
NachoMahma
NachoMahma

Best Answer 9 years ago

. The wall wart wires are an antenna and you are picking up stray voltage. If you put a load on the line, the voltage will disappear.

0
lemonie
lemonie

9 years ago


They have a smoothing capacitor in 'em which will hold a voltage, see also Nacho.

L