# How do I solve transformer numericals with additive polarity?

Ok, so for subtractive polarity in transformers(dots at the same side of the windings) E1/E2=N1/N2

But if it's subtractive polarity E1 and E2 are out of phase so shouldn't E1/E2=-N1/N2

Edit: Ok here is what I tried out. I just need to understand the first step. I solved the same question for a transformer with additive polarity

!

• You defined E1 as positive when current flows out of the left dot. Current flows in one dot and out the other. Therefore when E1 is positivve (current out of left dot) then current flows into right dor which makes E2 negative (i.e. oppposite of your defined polarity.) Some unnecessary negatives but it works. I recommend you define things so such negatives don't happen for straightforwardness. – DKNguyen Nov 20 '19 at 1:53
• BTW, your "additive" and "subtracted" polarity have no meaning...the windings are isolated. Nothing is adding or subtracting from anything. Stop thinking about it that way. The reference of one winding is completely independent of the reference of the other. If you pick the top right terminal to be the reference for the secondary, it doesn't suddenly change the polarity of the physical transformer's windings relative to each other. – DKNguyen Nov 20 '19 at 1:57