Wheatstone bridge arrangement with an ideal wire in middle

[_RisH_]

Homework Statement

I came across this questions in one of the online entrance tests,so i do not remember the exact values,I remembered the arrangement.
________________
|... |...|
|... A...C
2v...|--------| (Please ignore the dots,they are to prevent figure from getting
|....B...D distorted)
|________|_______|

A,B,C,D are resistances connected to a 2v battery.Rest everything are ideal wires.We have to find the current through the connecting wire(-----).

Let A-20ohms,B-15ohm,C-5ohms,D-10ohms

Homework Equations

V=I*R

The Attempt at a Solution

The current flowing in ---- wire will be the difference in potential across it divided by the resistance.But since it is ideal it has 0 resistance which gives infinite current.I am totally confused.(The answer is a finite value.)

 

[NascentOxygen]

Welcome to Physics Forums.

Forget about the bridge, just concentrate on determining the current in each resistor, first. Obviously, resistors A and C are in parallel?

 

[_RisH_]

Yes...but ignoring the bridge would mean (AseriesB)||(C series D) ri8?

 

[projjal]

Yes...but ignoring the bridge would mean (AseriesB)||(C series D) ri8?

No. It would mean (A parallel C) in series with (B parallel D). Calculate the current through the resistors and from this you can find the current through the bridge.

 

[NascentOxygen]

Yes...but ignoring the bridge would mean (AseriesB)||(C series D) ri8?

I'm not saying ignore anything, nor suggesting any alterations to the circuit. I'm suggesting that you not get hung up on it being any special arrangement or having any special name. Just analyse it as a 4 resistor circuit to determine the current in each of the 4 resistors. The connecting wire remains in place right where it is.

Your first step could be to determine the current drawn from the source, once you have calculated the effective resistance of that bunch.

Then we'll take a closer look ...

 

[_RisH_]

A||C-4ohms B||D-6 ohms. Equiv. resis.=10 ohms.So current drawn is .2 ampere.Is this correct?

 

[projjal]

A||C-4ohms B||D-6 ohms. Equiv. resis.=10 ohms.So current drawn is .2 ampere.Is this correct?

Correct.Now find the current through C & D (or A & B) and hence you will get the current through the connecting wire.