Basic Electrical theory : flow of charges and electrons

Thread Starter

HoopHoop

Joined Aug 22, 2016
24
It is said one coulomb of charge flow per second is known as one ampere of electric current.

Now if current is the speed of flow of charge then why the distance isnt mentioned?? How much distance a coulomb of charge needs to cover in one second to be valued as one ampere of electric current? How can the speed of charge flow be measured without distance being specified?

Also can anyone tell me how to private message another user?
 

AlbertHall

Joined Jun 4, 2014
11,217
Suppose you have a pipe with water flowing though it. Every second one gallon of water enters the pipe and one gallon of water leaves the other end of the pipe. The water flow rate is one gallon per second. This does not relate to the length of the pipe in any way.

Simiilarly with one 'gallon' of electrons flowing through a wire.
 

Thread Starter

HoopHoop

Joined Aug 22, 2016
24
thanks for helping. ofcourse length of pipe doesnt matter but i think the distance IS indeed mentioned and hides in the gallon itself.

gallon is a volume which is area X length, since area of the pipe is fixed the length of water flow in n out can be measured.

similarly in case of electrons, if the coulomb is known then the no. of free electrons is also known n if no. of free electron is known and the metal is known (suppose copper or aluminium) then we can know the 'volume' of the electrons which wud give the travelling length of the said electrons.
 

kubeek

Joined Sep 20, 2005
5,750
I don´t understand, why do you want to know the "volume" of electrons? or length they traveled? If there is 1A current, then through the wire comes 6.242×10^18 electrons every second.
Whether the wire is thick or thin, long or short, square or round is completely irrelevant to the fact that said number of electrons per second enters one side of the wire and exits the other.
 

Thread Starter

HoopHoop

Joined Aug 22, 2016
24
I don´t understand, why do you want to know the "volume" of electrons? or length they traveled? If there is 1A current, then through the wire comes 6.242×10^18 electrons every second.
Whether the wire is thick or thin, long or short, square or round is completely irrelevant to the fact that said number of electrons per second enters one side of the wire and exits the other.
Frankly speaking its because I'm really weak in this subject. There's no particular requirement other than trying to clear some confusion. I just cudnt understand how speed is mentioned without the mention of length.

the said no. of electrons has a charge of 1 coulomb so yes i understand ur point completely. thanks. :)
 

AlbertHall

Joined Jun 4, 2014
11,217
I just cudnt understand how speed is mentioned without the mention of length.
Rate of flow is not the same as speed.
Small stream in which the water is travelling at 4mph.
The lower reaches of the amazon in which (let's say) the water is flowing at 4mph.
The water is flowing at the same speed in both, but the flow rate (gallons per second) is massively bigger in the second case.
 

Thread Starter

HoopHoop

Joined Aug 22, 2016
24
Rate of flow is not the same as speed.
Small stream in which the water is travelling at 4mph.
The lower reaches of the amazon in which (let's say) the water is flowing at 4mph.
The water is flowing at the same speed in both, but the flow rate (gallons per second) is massively bigger in the second case.
flow rate is volume per second. speed is (axial) length per second.

since area is bigger in 2nd case flow rate = vol./sec = area * (length/sec) is higher.
 

BR-549

Joined Sep 22, 2013
4,938
Is water elastic or bouncy? Charge needs area, but not like water uses volume. Can you put 3 gals of water in a 1 gal jar?

We can adjust the number of charge per area or volume...........charge is compressible, water is not.
 

Thread Starter

HoopHoop

Joined Aug 22, 2016
24
Is water elastic or bouncy? Charge needs area, but not like water uses volume. Can you put 3 gals of water in a 1 gal jar?

We can adjust the number of charge per area or volume...........charge is compressible, water is not.
charge is not compressible either. in any volume water or charge can be sped up or down. if water has a certain speed in a bigger diameter pipe speed will increase when it reaches a smaller diameter directly connected to the bigger one. for charge it is also the same.

in a fixed volume of copper if there is X coulomb of charge then some extra charges cant be forced into the fixed volume to make it X + Y. its impossible. if the area of the conductor is reduced then charge flow will increase but in a fixed volume of water or metal extra water OR extra charge cant be forced into.
 

KL7AJ

Joined Nov 4, 2008
2,229
It is said one coulomb of charge flow per second is known as one ampere of electric current.

Now if current is the speed of flow of charge then why the distance isnt mentioned?? How much distance a coulomb of charge needs to cover in one second to be valued as one ampere of electric current? How can the speed of charge flow be measured without distance being specified?

Also can anyone tell me how to private message another user?
Unless the electrons are restricted to LAMINAR FLOW, it's almost impossible to define distance. The path of charges along a wire is ALMOST a random walk. :)
 

DGElder

Joined Apr 3, 2016
351
It is said one coulomb of charge flow per second is known as one ampere of electric current.

Now if current is the speed of flow of charge then why the distance isnt mentioned?? How much distance a coulomb of charge needs to cover in one second to be valued as one ampere of electric current? How can the speed of charge flow be measured without distance being specified?

Also can anyone tell me how to private message another user?
Speed is distance/time. Rate is a to-be-specified units/time.

Current is specified as the rate at which charge passes through a cross section of material or space.
 
Last edited:

be80be

Joined Jul 5, 2008
2,051
coulomb of charge flow per second is known as one ampere
It's the resistance that makes the changes big pipe lots of water little one not much comes out fast.
Same as with the wire big wire little resistance.
Big wire and bang one amps out where as little wire it takes longer to output a amp but both will as long as the wire can handle the load.
 

Papabravo

Joined Feb 24, 2006
15,730
Isn't that for atomically bound electrons?

A magneton nucleus physically explains this principle. For me anyhow.
It is for all fermions, aka particles with half integer spin. Bosons, aka particles with integer spin, are not so restricted and any number of them can be in the same state. The Bose Einstein Condensate would be the ultimate in compression.
 

Veracohr

Joined Jan 3, 2011
750
The speed depends on the material of the conductor but this doesn't affect the current. X number of electrons passing through a point is Y amperes regardless of how long they take to pass that point. And a "point", mathematically, has zero length.
 

kubeek

Joined Sep 20, 2005
5,750
The speed depends on the material of the conductor but this doesn't affect the current. X number of electrons passing through a point is Y amperes regardless of how long they take to pass that point. And a "point", mathematically, has zero length.
The crossectional area to be precise, the actual material does not matter.
 
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