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  An inductor is created when a conductor is wound with wire into a coil, with the wound wire resulting in the creation of a strong magnetic field per Ampere's Law. This magnetic field then induces a voltage, which resists the change in current that created it. When two or more inductors are coupled together, a transformer is created, which converts current from one voltage to another.
  
  

The Unit of Inductance

• The unit used to measure inductance in an inductor is referred to as the Henry (H), named after inventor Joseph Henry. Smaller units of the Henry include the millihenry (mH), microhenry (μH), and nanohenry (nH).
  
  

Factors Affecting Inductance

• Inductance is affected by a number of factors, including: how the coil is wound, the inductor's actual size/coil area, and the type and size of the core material used within the inductor. For example, an inductor with a greater number of wire turns will generate a greater magnetic field force. Also, a greater coil area represents less opposition to a magnetic field flux, thus resulting in a higher inductance, while a lower surface area creates more opposition and equates to less inductance.
  
  Two cores commonly employed in inductors are iron and powdered iron, though one feature common to all cores used in inductors is magnetism. Lower core magnetic permeability will result in lower inductance, with the opposite being true of higher core magnetic permeability.
  
  

DCR (DC Resistance)

• The inductor's DC Resistance is specified in ohms, and is the maximum wire resistance of an inductor. Inductors in a DC circuit are designed to minimize the DC resistance.
  
  

DC Inductor Types

• DC inductors are classified based on what core material is used within the inductor. While there are numerous core types, the most common ones found in DC inductors include air, iron, and ferrites.
  
  An air-type inductor differs from the others in that it does not use a magnetic material to wind its coil with, but instead uses plastic, ceramic, or some other nonmagnetic form. An iron core, on the other hand, can increase inductance by several thousand due to its higher permeability and increased magnetism. Ferrite cores are used when nonconductivity is desired, which disallows the flow of currents throughout the inductor.