# Need help on transformers

1. Jul 16, 2008

### sero2000

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

Given
R3= 10.0Ω
IR1= 2.0A

Prove that Vpri =30( 10R1+R1R2+10R2)/R2

2. Relevant equations

3. The attempt at a solution
Current across R2= 2xR1/R2
Current across R3= 2R1/R2 +2A
Total Voltage in sec coil= [2R1/R2 +2] x10 + 2R1
= 20R1+20+2R1R2/R2

Im stuck here currently=( any help?

2. Jul 18, 2008

### Ouabache

Is this the only information given? Are you sure the 2A current is through R1?

We describe current as going through an element (such as a resistor), rather than across it. Voltage, on the other hand, is measured across an element.

3. Jul 18, 2008

### sero2000

Yea the current through R1 is 2.0A. I already gt the answer=) apprently the teacher forgot to give the turns ratio for the qn. Thanks anyways=)

4. Jul 18, 2008

### Ouabache

I thought so, I was just about to add, unless this were an isolation transformer, I would expect a ratio of turns (N1:N2), voltage (Vp:Vs), or current (Ip:Is) to be given.

What was the turns ratio? (I'd like to solve this one too).

5. Jul 20, 2008

### sero2000

Oh the turns ratio was 15:1