I'm starting in electronics, and some measurements are surprising to me... Why i have the same V before and after a resistor? I've taken two photos to illustrate it, any advice will be very appreciated!

Thanks in advance!

measurement 1

measurement 2


simulate this circuit – Schematic created using CircuitLab

  • 1
    \$\begingroup\$ There's only a voltage drop across a resistor if there's a current flowing through it. Have you completed the circuit to allow current to flow? \$\endgroup\$
    – brhans
    Mar 8, 2016 at 12:08
  • 2
    \$\begingroup\$ You need to show a schematic of each measurement, it's not possible to guess what you're measuring from the photos, nice though they are, edit your post and use the schematic button. \$\endgroup\$
    – Neil_UK
    Mar 8, 2016 at 12:08
  • \$\begingroup\$ note: both measurements use the red tester in same wire (left). Black tester moves from left to right wire on resistance. \$\endgroup\$
    – user675319
    Mar 8, 2016 at 12:09
  • \$\begingroup\$ The circuit is similar to it, difference is I don't have a led. I have two simple wires, but in essence the question is: Why I get the same V value before and after resistor? I't browen, or not working? \$\endgroup\$
    – user675319
    Mar 8, 2016 at 12:26
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    \$\begingroup\$ "The circuit is similar to it" doesn't quite cut it when it comes to electronics. You're getting the wrong result when measuring and the circuit is correct so there's obviously an important difference between the circuit and reality. To help you we need to know exactly how everything is connected. \$\endgroup\$
    – pipe
    Mar 8, 2016 at 12:35

1 Answer 1


The resistor is only connected to the negative rail. The other side of resistor, which is on the central board area (I have no idea what that area is called) is not connected to anything.

On a bread board, the power rails (the strips of 2 that run vertically) are connected. On the central plains, the strips are connected horizontally. There does not appear to be a connection between the red jumper and the resistor.

Here's a bit more information on exactly what makes up a bread board: https://learn.sparkfun.com/tutorials/how-to-use-a-breadboard

  • \$\begingroup\$ Oh I see, what a dumb mistake...So circuit is not closed! I'll try when I arrive home, thanks for the explanation! \$\endgroup\$
    – user675319
    Mar 8, 2016 at 12:53

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