Can we have current without voltage?

[engrbabarmansoor]

can we have current without voltage?

 

[the_risk_master]

Re: current

Of course (SURE!!!), we can have current without voltage...

For example, we shorted a DC source (a battery) to bypass a load, we coun get zero voltage by Ohm's Law (remember?) I=V/R, at shorted condition R=0 Ohms, so we get I=V/0, then I would approach to a very lage value (upto infinity), but that was mathenatically (it assumes a zero internal resistance to the source), but in actuality internal resistance exists (copper resistance from wires and connectors are additional to this), even though shall we say the battery is "supercooled" still resistance exists. Okay nevermind about the resistance discussion, so now we proved it that current may exist even voltage is not present (for thoeretical approach)

 

[IanP]

Re: current

The answer is: NO ..
If there is no potential difference - there is NO current ..
As an analogy, take two tanks full of water and connected with a pipe .. If you position them at the same hight - what will happen - nothing !!!

Regards,
IanP

 

[the_risk_master]

Re: current

Hi Sir Ianp,

Why not? for theoretical analysis, example; a shorted DC source
R=0 ohms, by Ohm's Law, V=IxR, so V=0 volts, but equating for I (current)=V/R and I--> infinity

Am I wrong?

 

[IanP]

Re: current

Nothing divided (or multiplied) by whatever is still nothing ..

Regards,
IanP

 

[srieda]

Re: current

Hi Sir Ianp,

Why not? for theoretical analysis, example; a shorted DC source
R=0 ohms, by Ohm's Law, V=IxR, so V=0 volts, but equating for I (current)=V/R and I--> infinity

Am I wrong?

This is like the old mathematical puzzle...
you are saying that I = V/R = infinite because R=0..
But when you have a short, V also is eqaul to zero... So I in this case is
I = 0/0 ........... undefined...

I totally agree with IanP... current cannot exist without a potential difference...

 

[Kral]

Re: current

engrbabarmansoor,
For DC current, I agree with IanP: "NO...". However, on an instantaneous basis the condition of current flow with zero voltage is possible. Consider a capacitor that is driven by a sinusoidal voltage source. The current leads the voltage by 90 deg. Therefore when the current is at its peak value, the voltage is zero. This is true, of course, only with an ideal capacitor.
Regards,
Kral

 

[artem]

current

For case when current is induced by external field , let say short circuited photodiode is radiated by photons you get a current without visible potential difference. If photodiode leads were made of superconductor it is not possible to measure potential difference.

So what a potential taken from any point on superconductor made circle placed into changing magnetic field ?

P.S. Of course the case is ideal , at least till now)

 

[shg]

current

Current flow is not a result of potential difference.
Potential difference (or voltage drop) is a result of current flow.
To make a potential difference first of all there's need to be current flow from one point to another, which will move some charged particles (ions, electrons, or whatever). But if theres a potential difference it doesn't imply a current flow.
If You take it that way, You can have a current without voltage (also voltage whithout current). Superconductors are a very good example here.