Current always goes in the less resistance path

Hi,

I read in a book that "Current always goes in the less resistance path". In a paralel circuit with 1k resistor to one side and 10k resistor to another side the current still goes in both sides. Why does the current goes to both sides? It should only go to the 1k resistor cause there is less resistance.

In the same paralel ciruit, if I add another wire in paralel to the ground all the current will go to the ground, proving that "Current always goes in the less resistance path". But why does this "law" only work when one of the wires is ground?

It seeks the path of least resistance.

I read in a book that "Current always goes in the less resistance path". In a paralel circuit with 1k resistor to one side and 10k resistor to another side the current still goes in both sides. Why does the current goes to both sides? It should only go to the 1k resistor cause there is less resistance.

Ohm's Law applies to both resistors. If the resistors are in parallel, the same voltage will be applied to both resistors. The 1k resistor will have 10 times the current of the 10k resistor.

If you were to supply a constant current (somewhat unusual in the real world) the current will divide in inverse proportion to the resistance with most of the current going through the lower-value resistor. (Of course, the same voltage would still be applied to both resistors.)

But why does this "law" only work when one of the wires is ground?

You don't need a ground, but current won't flow unless you have a "complete circuit" with a current path back to the power source.

I read in a book that "Current always goes in the less resistance path".

There can be confusion when you try to simplify [u]Ohm's Law[/u], which precisely & mathematically describes the relationship between voltage, resistance, and current, and [u]Kirchhoff's Law[/u] which precisely & mathematically describes how voltages & currents divide (or sum) in series and parallel circuits.

gilperon:
Hi,

I read in a book that "Current always goes in the less resistance path". In a paralel circuit with 1k resistor to one side and 10k resistor to another side the current still goes in both sides. Why does the current goes to both sides? It should only go to the 1k resistor cause there is less resistance.

In the same paralel ciruit, if I add another wire in paralel to the ground all the current will go to the ground, proving that "Current always goes in the less resistance path". But why does this "law" only work when one of the wires is ground?

In a 101 class, you would be told that electric current is like water: so think about a very large storage tank having a 10 cm pipe and a 1 cm pipe for water to flow out. Does the existence of the larger pipe prevent water from also seeking and flowing from the smaller pipe. No. Water flows from both pipes, but more water flow from the larger pipe.

The diameter of the pipes act like resistance. The height of the water tank affects the water pressure at the ground end of the pipe (column of water analogy) and water pressure is analogous to Voltage.

Unless your shorting wire is a perfect connector (it is not) then a very small current will still flow through the resistor... It may be too small to measure on your common VOM or DVM, but precision lab equipment will be able to pick up the existence of the current flow.

BOOKS sometimes make complex concepts so simple that the book represents a misconception.

Ray

I read in a book that "Current always goes in the less resistance path".

That book is wrong. It is a myth.

Current flows through all available paths. The amount of current through each path is inversely proportional to the resistance of each path.
Simple as.

In the same paralel ciruit, if I add another wire in paralel to the ground all the current will go to the ground,

No it does not.

What happens is that the internal resistance ( well impedance actually ) of the power source limits the total amount of current and you get a voltage divider action between that resistance and the very low resistance so called "short circuit wire". This reduces the voltage across the resistor to an amount technically known as "bugger all", which in turn reduces the current through the resistor to a similar magnitude, making it appear no current is flowing through the resistor, but that is only because there is "bugger all" voltage across it. This is what leads ignorant people to say that current always goes in the less resistance path. This, using another technical term, is known as "bollocks".

Current always goes in the zero resistance path. :art:

LarryD:
Current always goes in the zero resistance path. :art:

No it goes in ALL paths.

LarryD:
Current always goes in the zero resistance path. :art:

Only at absolute zero!

But at temperatures above absolute zero, there is no perfect zero resistance- therefore as I stated previously, current goes into all branch circuits. Same as stated by G_M.

Ray

Of course I was referring to absolute zero for zero resistance :art:

Yeah, and what if there are 2 zero-resistance paths in parallel?

Grumpy_Mike:
...
This reduces the voltage across the resistor to an amount technically known as "bugger all", which in turn reduces the current through the resistor to a similar magnitude, making it appear no current is flowing through the resistor, but that is only because there is "bugger all" voltage across it. This is what leads ignorant people to say that current always goes in the less resistance path. This, using another technical term, is known as "bollocks".

ROFL - if only all books were written like this, it would make it so much easier and enjoyable to learn. That's cheered up my Sunday morning, thanks :smiley:

Put a pin prick in a fire hose, and water will spray out of it. But the lion share will still come out the huge nozzle at the end.

Superconductivity (zero resistance) occurrs at temperatures well above absolute zero. Not yet as high as room temperature, unfortunately, but hopefully one day this will be achieved. Then there will be a revolution!

oric_dan:
Yeah, and what if there are 2 zero-resistance paths in parallel?

Then you may have created a singularity!

gilperon:
I read in a book that "Current always goes in the less resistance path".

One might be inclined to suggest you throw that book away.

What might be equally useful, would be if you can cite the book and paragraph. One suspects that what you imagined the book said, may not actually be what it said.

it quite often happens in medical practice, that the patient's recollection of what the doctor said, bears little resemblance to what the doctor did say - and some very creative realities come from this game of "Chinese Whispers".

gilperon:
Thank you so much!!! I thought that current indeed flow in the less resistance path despite my observations in a paralel circuit where both leds light up.

I have three final question:

if I have 2 ground wires in paralel and nothing else, will current flows on both?
if I have 1 ground wire in paralel with another wire with a resistor. Will current flow in both wires too as all you said? When I create this circuit my led in the resistor wire will not light up. Why?
what is ground? Why do I need to plug always my circuits to gruond? Where is arduino ground connected since I didnt connect my arduino to earth?

Even wire has resistance. Just use ohms law to calculate the current. Put a piece of wire in parallel with a resistor and the resistor will still conduct but excedingly little.

PLEASE. Just read ohms law. All will be revealed.

gilperon - do you ever read the answers before you ask a question?

Why do I need to plug always my circuits to gruond?

You don't you need a circuit for the current t flow round.
Read:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

When I create this circuit my led in the resistor wire will not light up. Why?

Read what you have been told and try and understand it.

Grumpy_Mike:
You don't you need a circuit for the current t flow round.
Read:-
Power Supplies

Mike, can you explain that a little more please. Which paragraph on your link explains what you mean?

Which paragraph on your link explains what you mean?

It is the two diagrams at the end.

I was answering:-

Why do I need to plug always my circuits to gruond?

Which of course you don't need to.

There is no need for a connection to "the ground" or earth as we say in the UK. You just need a common point in two independent systems to allow current to flow.

The OP is confused by the term ground, he thinks it means the physical ground and not just a common reference point.