This may seem like a stupid question for someone who's been in electronics for a long time, but I need to understand this. How do you know what the effect of a short will be on a resistor? I am using Thevenin's theorem to figure out load voltage and current, and I have a problem where I've removed the load on the right side (verticallly drawn resistor) and am trying to figure out total resistance. To check the resistance I am starting from the top right side and I have a point where there is one vertically drawn resistor, a horizontally drawn resistor, then another vertically drawn resistor, then the voltage source has been replaced by a short (which means I have 2 parallel,and a series resistor, and then a short in parallel with the parallel resistors.) The book says that the resistor closest to the short is shorted out, but the other parallel resistor isn't. How can that be? How do the electrons know that there is less resistance at the other end? I thought some electrons will go through any resistance. Shorts make sense when there is a direct path back to the source, but not when there are resistances in between. The resistors are R1-10 ohms (first vert. resis. on the left), R2-20 ohms (horiz. resis.), R3-20 ohms (vert. resis. on the right) Thanks for your help.