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Electricity

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23 Dec 2007 17:11:45 IST

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510

Electric Potential.

None

Just a few days back my friend told me that even if the PD is zero , current can flow through a wire.

He told me that any two points on a wire are at same potential and still current flows through them.

Then , why does current now flow through a wheatstone's bridge

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Purav Master

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23 Dec 2007 19:30:07 IST

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Actually the two points on wire are at same potential only theoretically.

Every wire has some resistance that causes the potential drop. So those points would be at different potential and so current flows under the influence of this pd.

If you see theoreticallt then you may be confused in the way we draw circiuts.

Actually in all theoretical circuits there is no pd between wires. And so actually the whole wire is just an elaborated form of a point at a particular potential. We draw long wire-like structure just to have a clear representation of a circuit.

Remember that if in a circuit you have two points connected by a 'wire' with no resistance in between you can joint the ends and treat them as a single point.

Neeraj Agarwal

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23 Dec 2007 21:42:07 IST

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Actually the resistance of the wire is assumed to be 0 in all cases of such circuits...

and thus the pd is also 0...

when u apply kvl in some circuits u may notice that even when the potential is 0...current flows....

an explanation to this is...
as I = V/R...and V is 0....and note that R is also 0....so I is of a 0/0 form ...so we can't predict the value of I because its an indeterminate form...

my physics teacher himself raised this question and gave the explanation...so i m sure that its correct....
i had written this thing in a post some time back but many goiitians don't agree...

but i think its correct....

abc def

Hot goIITian

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24 Dec 2007 18:33:17 IST

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Is V always equal to IR???. Please give me an answer. Haliiday dosen't says so!

abc def

Hot goIITian

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24 Dec 2007 18:35:08 IST

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As you said that when V = 0 R = 0 , please tell me wrt to a wheatstone's bridge. The galvanometer has some resistance , doesn't it?

Umang

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24 Dec 2007 19:35:38 IST

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Hey !
I also had this doubt initially.
the thing is that though there is some resistance in the wires, we ignore it to make calculations simpler !
if potential difference is ZERO, no current can flow.

disha gupta

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25 Dec 2007 20:14:20 IST

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its a veryyyyy nice question raised!

look...

FIRSTLY

in jee syllabus we dont hv dynamic resistance n only static resistance is thr...

therefore V=IR

SECONDLY

when PD=0 then current flows only when R=0...

WHEN R is not equal 2 zero n V=0 then I has 2 b zero(as is d case of wheatstone bridge)...

i hope i could make it clear!

sheva ......

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25 Dec 2007 20:36:27 IST

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yeah i had the same question. in fact posted a topic on this question.still not sure

Neeraj Agarwal

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25 Dec 2007 20:51:20 IST

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we do not consider resistance in wires.....never....

we always assume that resistance of wire is 0...and there is no chance of even thinking that there may be some resistance in the wire so that there is some pd....

Neeraj Agarwal

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Joined: 22 Jan 2007

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25 Dec 2007 20:53:36 IST

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