# Mesh Current Analysis

1. Feb 18, 2014

### Tekneek

1. The problem statement, all variables and given/known data

I need to find the Current through short circuit wire (between a and b).

2. Relevant equations

All the resistor values are same, 100 Ohms
V1 = 5V
V2 = 10V

3. The attempt at a solution

Loop A
ia*(R2+R4+R1) - ib*(R4) = 5

Loop B
10 + (ib-ia)*R4 + ib*R3 = 0
ib*(R4+R3) - ib*R4 = -10

After plugging in all the values,

300ia - 100ib = 5
-100ia + 200ib = -10

ia= 0, ib= 0.05 Amps

Current through the circuit is same as ib because the current is not going to flow through R5.
But the problem is I don't think it is possible for ia to be 0...

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2. Feb 18, 2014

### Staff: Mentor

That looks right.

If V2 were much higher, say 60v, it would be forcing current into source V1, similar to charging a battery. So there is some point where V1 ceases to supply current, but before its current goes negative. This point occurs when V2=10v here.

Yes, the current in the s/c is that current in R3.

3. Feb 18, 2014

### Tekneek

Thanks. But how does V1 stop supplying current?

4. Feb 18, 2014

### Staff: Mentor

When it finds itself connected to a voltage that's exactly equal to its own voltage. Current can flow neither IN nor OUT.