A transformer is a static electrical device that transfers energy by inductive coupling between its winding circuits.

 A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a 

varying magnetic flux through the secondary winding. This varying magnetic flux induces a varying electromotive 

force (emf) or voltage in the secondary winding.

Transformers range in size from thumbnail-sized used in microphones to units weighing hundreds of tons 

interconnecting the power grid. A wide range of transformer designs are used in electronic and electric power 

applications