# Transformer Characteristics

#### USNtron75

Joined Dec 14, 2010
12
If you will, consider a 120 VAC power transformer that steps down to 12 VAC with a center-tapped secondary winding. Now, I understand why there's 12 VAC at each of the outside lines, but why is is the voltage cut in half on the ceter line? Does the coil impede (build pressure) the voltage, thereby cutting it in half at the center line? Ultimately, what determines the available voltage on the secondary side? Is it the ratio between the primary and secondary sides? Thank You!!

Einstein said, " I just want to learn to think like God. Everything else is details. "

Tron 75

#### SgtWookie

Joined Jul 17, 2007
22,230
Is it the ratio between the primary and secondary sides?
DING! DING! DING! We have a winner!

It is the ratio of turns from the primary to the secondary side.

If you have a 120v primary and a split 12v secondary, then the primary has 100 turns to the secondary's 5 for each side of the center tap.

#### Yako

Joined Nov 24, 2011
245
Don't forget to tell them about eddy loss current. How does the voltage magically transfer between the windings too?