Magnetics

Magnetic, in general, refers to any electronic device that employs the use of magnetic fields to accomplish its intended purpose. The classic circuit component that converts electrical energy to magnetic energy (and vice versa) is the inductor. Thus, the inductor has electrical properties that are unique in nature. Because of this, the inductor is a critical component of analog filtering, and inductive coupling is the fundamental principle behind the transformer.
Although digital signal processing (DSP) has become more popular, out of simple necessity the analog signal filter is still widely utilized in countless applications. Inductors (along with capacitors) are the two types of energy-storage components used in the design of analog filters. Together the inductor and capacitor can be used to remove high-frequency components (lowpass filter), remove low-frequency components (highpass filter), remove only a specific frequency range (bandstop) or pass only a specific frequency range (bandpass).
Transformers are essential to the distribution of AC power. But transformers are nothing more than two inductors with strong mutual coupling between them. Step-down transformers reduce the voltage from the input power source to an amplitude that is less dangerous and also more practical in businesses and households. In contrast, step-up transformers increase the voltage for more efficient transmission over long distances of power lines.