In 1836, the Reverend Nicholas Callan of Maynooth College, Ireland, revolutionized electrical transformers with his invention of the induction coil. He astutely observed that increasing the number of turns in the secondary winding relative to the primary winding resulted in a higher electromotive force.
Induction coils emerged as a result of scientists and inventors looking for higher voltages from batteries, which inherently generate direct current. To induce the necessary flux changes, these coils relied on vibrating electrical contacts, intermittently breaking the primary current. The period from 1830 to 1870 witnessed persistent efforts, largely through trial and error, to improve induction coils, ultimately revealing the fundamental principles of transformers.