I got confused about this question~~! for some advice

[ZengLei]

i'm reading the books about the basic electirc thoery.
and when i learn the OHM's law,and Kirchhoff's law
i design a circuit V1=V2=V3)

we know that V1/R=i1+i2
and what makes me confused is the value of i1 and i2 respectively??
(i2 is the current through the short circuit,and the voltage resuorce is ideal...)
i think it is hard to determinate the current i1 and i2.......
would someone give me a detailed explanation,thanks ! :?:

 

[jayc]

As shown in your figure, V2 and V3 are placed back to back, meaning the voltage difference across the two outer terminals (V2+ and V3+) is 0. Assuming ideal voltage sources, this implies that the current path through V2 and V3 is also effectively a short circuit. Therefore, it is not really significant to determine the currents through the two branches individually.

However, if there are non-idealities (wire resistance, series resistance for voltage sources), then we can easily determine the corresponding currents through each element.

 

[ZengLei]

Therefore, it is not really significant to determine the currents through the two branches individually

that's what makes me confused!!!!
Don't we really have any way to determine the currents through the two branches individually?!!!
Or there is something wrong with the LAW??

 

[amit kumar]

in this problem, consider the branch in which 2 voltage sources are placed as they are in opp. polarity current i2 is zero also we can verify by v=ir,here r=o.in above loop apply v1=i1r

 

[jiveshgovil]

i'm reading the books about the basic electirc thoery.
and when i learn the OHM's law,and Kirchhoff's law
i design a circuit V1=V2=V3)
we know that V1/R=i1+i2
and what makes me confused is the value of i1 and i2 respectively??
(i2 is the current through the short circuit,and the voltage resuorce is ideal...)
i think it is hard to determinate the current i1 and i2.......
would someone give me a detailed explanation,thanks ! :?:

Since i2 flows through the short circuit branch. The current through it is V1/R. Current i1 is zero. This means all the current flows through the short circuit branch. because it offers no resistance. The loop containing the battery may offer some battery resistance, so current prefers to flow throught the branch that offers no resistance i.e. the short circuit branch.

 

[kaustubhkhole]

You cam solve each circuIt separatelY and then aDD then UP.......

 

[jallem]

If you take out the short, the current is zero.
In others words, even if you have zero potential
between the two nodes is a high impedance.That
is the trick. So, the current I2 is V/R and I1 is zero

 

[jayc]

If you take out the short, the current is zero.

I see several people are claiming that the current i1 is zero. This is not true. Given ideal voltage sources, the series resistance is 0. The back to back voltage sources then act as a short circuit as well. You essentially have two ideal wires connected in parallel.

I supposed you could say that since both paths offer 0 resistance, half of the current goes through each branch. However, I say that this measure is insignificant because you will never achieve a situation where you have two ideal wires in parallel.

In normal circuits, wire resistance can usually be ignored because the resistors in consideration are much larger than the wire resistance. However, if you were to apply some voltage across two parallel (non-ideal) wires, the small wire resistances become very imporant and it is simple to calculate the respective currents through each.

 

[ZengLei]

yes,i said that the voltage source is ideal,without resistance.
So i wnat to get a accuracy result about the current
i1 and i2!!
can't we get the value of the two currents under the ideal condition?????

 

[easternbean]

develop you circuit model in some simulation software such as matlab or spice,then use the scope,you can get it !

 

[benzwishc]

as i see the component of v2 and v3 is just to constrain the current across the branch(v2,v3), we can have an alternitave circuit diagram to think of the problem, in the alternitave circuits we have three branch circuits to calculate the answer, i here do not calculate it personally,it is just my idea about the problem\]

 

[ZengLei]

May be this one is right

He said " the currents I1 & I2 are both indeterminant since V2 + V3 = 0 and assuming that there is no resistance in the wires, then I1 = 0/0 and I2 = 0/0"

Right?

 

[mohammad mokhtar]

Dear friend
in any circuit to have a certain current you must have a voltage difference to drive that current. In case of a voltage difference =0 volt you will have a zero current so if you connect 2 voltage sources back to back there will be a net voltage equal to zero then the derived current will be zero. I know why you are confuced you don t feel our answers to feel it : if you have flash light that works with 2 batteries if you reverse any battery the flash light will not work because the net voltage is 0 hence the current is zero then it will not light. I hope I made my self clear enough for you

 

[ZengLei]

thanks all

Added after 4 hours 32 minutes:

Well,i think i could get the result from the pictrue below>>>