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# Why are resistors placed on the ground side of a circuit? Answered

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## 6 Replies

mpilchfamily (author)2012-06-07

What circuit are you referring too?

If you talking about a basic power source, resistor, and LED then it doesn't really matter which side of the circuit you place the resistor on.

porternick (author)2012-06-13

[-]-------/\/\/\/\/------LED--------[+]

Why does it not matter what side of the LED the resistor is on? What are the conventions for knowing where to place a resistor?

I am wondering if I am missing a conceptual understanding of current. I think of it using the plumbing analogy that the "current" is coming from the [+] side of the circuit. If this is the case, why wouldn't you want the resistor on the [+] side reducing the current going into the LED?

[-]-------LED------/\/\/\/\/--------[+]

mpilchfamily (author)2012-06-13

Simple circuits like that it doesn't matter what side the resistor is on. The resistor is there to limit the current to the LED and it can do that from either side of the LED.

But as a means to standardize schematic layouts and circuit design the resistor is commonly placed on the negative side.

porternick (author)2012-06-13

Thanks for discussing this with me. I am really interested in the why and how of it? Why does it go on the ground side? If the current is from the positive end, how is it limited on the negative end (after) the LED?

mpilchfamily (author)2012-06-13

The Resistor will limit the flow no matter which side you put it on. Look at it like a stream flowing in a continues loop. If you place a sponge anywhere in that loop the flow of the entire loop is effected.

In a way a battery will pull and electron from one side and release one on the other. When the flow is slowed by a resistor the electrons heading back to the battery are running slower so the next electron in line to be sucked into the battery isn't there as fast so the next one to be pushed out comes out slower as well.

Maybe a better example would be a set of balls in a track. The resistor is an open space in the track which will hold the balls back and delay them from moving along. The battery is a crank that is pushing the balls around the track. Since the resistor is holding 1 ball up its not pushing the rest of the balls so the next one can fall into place for the battery to push along again. Thus slowing the entire flow no matter where it is in the small circuit.

porternick (author)2012-06-13

Fantastic. This analogy makes much more sense to me. I appreciate the time you have taken to share your understandings with me. Happy making!