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Physics/The Path of Least Resistance

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Question
I'm sure you have heard the common phrase "electricity follows the path of least resistance."  I was wondering if this phrase is accurate.  If it is, how does the electricity "know" which path is the least resistant.  For example: A person's right leg (from the knee down) is completely metal (less resistant than the other leg).  Would the electricity tend to travel through the right leg, and if so, how would it "know" that the right leg would be the path of least resistance overall?  Thank you for your time.

Answer
Hello Ben,

Yes I have often heard that. It is not literally true. I would say that "the path of least resistance carries more current than paths of higher resistance." Some of the electrons will find their way to paths of higher resistance.

Imagine an elevated tank of water with 1 large diameter pipe and 1 narrow pipe to let water flow out and down. Open the valves for both pipes. Does all the water flow out the large diameter pipe while the narrow pipe delivers no water? No. Both pipes allow water to flow the best of their ability. How do the water molecules know which path to take? If the entrance to the large diameter pipe is all jammed up with other molecules, why not try this other one?

If you wire a 10 ohm resistor, a 12 ohm resistor, and 10,000 ohm resistor in parallel with each other and put this combination across a 12 V battery, the voltage across each of them will be 12 V. Therefore the current through them will be:
Current thru the 10 ohm resistor = 12 V/10 ohm = 1.2 amps
Current thru the 12 ohm resistor = 12 V/12 ohm = 1 amp
Current thru the 10,000 ohm resistor = 12 V/10,000 ohm = 0.0012 amps
The total current flowing through the combination is 2.2012 amps.

I hope this helps,
Steve
Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment Thank you very much. Your explanation (especially the water example) was very clear and helpful.

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Steve Johnson

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I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.

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I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

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BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University

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