# A very simple question about ohms law

Discussion in 'General Electronics Chat' started by kiloman, Sep 30, 2009.

1. ### kiloman Thread Starter New Member

Sep 30, 2009
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hey everyone

i was going over my basic electronics from scratch, and i was going over ohms law. well i understand the simplicity behind the law and how voltage, current, and resistance are all related, but i started thinking about what if resistance was 0... so there would be no voltage or current right? well when i try to visualize this, 0 resistance would mean there is no resistance for the electrons to pass through. so how can there be no voltage or current? like if we took a copperwire and connected it from the + to the -, then it would be a short circuit. wouldnt there be a voltage and current still? even if for a brief period of time before something bad happens? maybe im thinking the wrong way? let me know! thank you

2. ### Voltboy Active Member

Jan 10, 2007
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In the case of the copperwire short circuit, there IS resistance, little but there is.
It happens that a superconductor has almost 0 resistance, so little that its negligible, and that's why it is so interesting and many researchers are trying to find a way to create superconductors at normal temperatures. I actually don't know how Ohms law applies to superconductors, try a google search for it.

3. ### wr8y Active Member

Sep 16, 2008
232
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In a real world circuit, if you applied any voltage to a resistance of zero ohms, you would have no voltage across the zero ohms, but your current would soar to the maximum value the battery or other source is capable of supplying. (That is to say, the current would be limited by the "internal resistance" of the source).

The only limit on the current would be how much current it takes to burn your conductors open OR, again, the maximum amount of current the supply can supply.

4. ### Wendy Moderator

Mar 24, 2008
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Pure theory, you would have infinite current and zero volts. Same thing you get whenever you have zero in a algebretic equation. Somewhere there would be resistance though, if only in the battery (and right before it explodes into a ball of fire).

5. ### bountyhunter Well-Known Member

Sep 7, 2009
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There is zero resistance in superconductors at temps of absolute zero. There would be current flow, but there would be no voltage developed across the resistance because there is none. In effect, you can have current flow without any electromotive force (Volts) to push the current.

It sounds impossible, but that's what relativistic physics predicts and it has been demonstrated.

6. ### TheWeasel New Member

Aug 28, 2009
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For this part of your query, I'm sure you could have 0V = 0I x 0R by having a supercooled silver 'ring donut' as a circuit with very close to no resistance, passing no current, because there's no voltage difference anywhere in the 'circuit'.

For your other point, I agree with other posts....i.e a big spanner across your car battery terminals would end badly, but for the microsecond before the spanner explosively melts, the current would be limited (slightly) by the internal resistance of the battery.

Last edited: Oct 8, 2009
7. ### Ratch New Member

Mar 20, 2007
1,068
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bountyhunter,

Perhaps, but at what current? Could a superconductive material sustain its superconductivity at high current levels? Has absolute zero been reached in the lab yet. I suspect the answer to both the above questions is NO.

You really mean charge flow. The is a big difference between a infinitesimal amount of resistance and none.

How would the charge know which way to flow without a voltage present?

How does relativity tie into superconductor physics?

Ratch

8. ### rjenkins AAC Fanatic!

Nov 6, 2005
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Superconductors are quite widely used in scientific and industrial applications.

There are a few metals that are supeconductors at liquid helium temperatures, and an increasing number of 'high temperature' materials that 'only' need liquid nitrogen.

One common application is superconducting magnets. A coil of superconductor has a connecting / shorting link that can seperately be temperature controlled.
This is warmed, a current is fed through the main magnet coil and once that is at the desired level the shunt link is cooled again. Once the whole thing is superconducting again, the power is disconnected.

The current cannot change without changing the magnetic field, and the interaction between the two is such that they both stay constant for very long times.

A few bits of info: