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### Topic: Resistors (Read 1 time)previous topic - next topic

#### low5545

##### Aug 25, 2011, 11:20 am
What is the difference between the two connections of resistors below? Which is more recommended?
arduino-freelancer.blogspot.com

#### Noorman

#1
##### Aug 25, 2011, 11:26 am
There is no difference, they are in the same chain, connected in series.
2B || !2B

... bonding electrons and bits!

#### Bill_Kerr

#2
##### Aug 25, 2011, 04:59 pm
Hi Lo5545

Absolutely no difference in operation.

If you were to measure the voltage from the mid point of either circuit (between resistor and lamp) to the -ve supply terminal, then you would see a difference, unless the lamp resistance was equal to the resistor.

Rgeards  Bill
Don't you just hate ONE D 10 T problems?

#### spirilis

#3
##### Aug 25, 2011, 05:29 pm
No difference, however as we often design circuits with negative side considered "ground" with our loads connecting straight to that for simplicity sake, it's logically preferred to put preparatory pieces of the circuit (i.e. resistors) on the positive side.  No functional reason, just a mindset thing (there is no spoon... LOL)

#### MarkT

#4
##### Aug 25, 2011, 10:49 pm
Yes, basically when analysing a circuit like this we make the assumption that the current round the circuit is the same everywhere, and all the voltages round the circuit sum to zero.  The circuit equations don't know or need to know what order the components are round the circuit.

When we consider alternating currents these assumptions start to break down (especially at high frequencies where the wavelength becomes comparable in size to the circuit itself).
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### Grumpy_Mike

#5
##### Aug 25, 2011, 11:52 pm
As others have said the two are identical. An analogy would be topology where shapes describer in terms of a stretchable rubber sheet.

Electrical topology is also important and a circuit is defined fundamentally by it's topology.
In this topology elements in series can be considered as one element with just the end points being important.

Joke:-
What do you call a man who can't tell the difference between a doughnut and a tea cup. -- A topologist

#### westfw

#6
##### Aug 26, 2011, 02:42 am
Quote
we make the assumption that the current round the circuit is the same everywhere

That's not an "assumption"; that's a fundamental law of physics...

There can be slight practical or stylistic reasons for setting things up one way or the other, if you're talking about the usual situation of a microcontroller pin, resistor, LED, and some power rail.  They're subtle enough that I don't remember the arguments.  (sometimes one arrangement will work out significantly better in a PCB design, for instance.)

#### retrolefty

#7
##### Aug 26, 2011, 05:02 am
http://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws

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