Eddy current
In experiments with an early induction coil in 1837, he found that replacing the solid iron core with a core made of a bundle of parallel iron wires greatly increased the output voltage. As was later discovered, this was because the divided core prevented eddy currents from flowing in the core. Eddy currents, circular electric currents induced in the core by the changing magnetic field, cause power losses. The technique of a "divided" iron core was used in all subsequent transformers, and is still used today in the form of laminated cores in transformers and powdered iron cores in inductors. Bachhoffner can thus be credited with the invention of this method of preventing eddy current losses.