# Classical Physical Explanation for Turn Ratio in Transformer

 P: 3 Hello. I'm trying to understand why, in terms of Maxwell's Equations, the ratio of the number of turns in a transformer converts an input voltage to an output voltage. EE explanations only seem to go as deep as this article: http://en.wikipedia.org/wiki/Transfo...sic_principles They state that the ratio of the input voltage to output voltage is determined by the number of turns in the primary and secondary coil. But why? What's actually happening to various field lines to change voltages?
 Mentor P: 11,837 Have you studied electromagnetic induction?
 P: 3 Yes, but not in the usual way. I'm familiar with maxwell's equations and all of that notation, I'm just trying to analyze this part in those terms. I'm looking for someone to explain in terms of the mechanisms of induction, preferably with calculus. Is there a way I can further refine the question to get more help?
P: 107
Classical Physical Explanation for Turn Ratio in Transformer

 Quote by scipioaffric Hello. I'm trying to understand why, in terms of Maxwell's Equations, the ratio of the number of turns in a transformer converts an input voltage to an output voltage. EE explanations only seem to go as deep as this article: http://en.wikipedia.org/wiki/Transfo...sic_principles They state that the ratio of the input voltage to output voltage is determined by the number of turns in the primary and secondary coil. But why? What's actually happening to various field lines to change voltages?
An alternating current will create magnetic and electric field components around the wire. Magnetic field component produced by input is transferred (carried like waveguide) to secondary winding (output) via a ferromagnetic core. Inversely, secondary winding is exposed to magnetic fields carried by ferromagnetic core and induces back a current at open terminals of output. Core is the physical link to carry magnetic fields. Turn ratios determine voltage ratio because at each turn you roll more, you will be exposing more wire length to the magnetic field.