• It provides support for its windings
• Core provides the medium to concentrate and contain magnetic flux 

DC through coil

• When a DC voltage is applied to the winding 
• Due to low resistance, the winding acts as a short circuit across the terminals of the DC source 
• Lead to the flow of heavy current through the winding resulting in overheating of the winding
• No Magnetic flux will generate. since DC does not have zero frequency

AC through coil

• When a AC voltage is applied to the winding 
• Produces a self-induced emf opposing the emf that initially set up the current
• Generate a magnetic field in the clockwise direction
• For an ideal inductor of zero ohmic  resistance, the back emf is equal and opposite to the applied emf.
• The induced current  generates due to a changing magnetic field.

Disadvantage of inductor

• The inductors of high inductance value are not possible. It is in large size
• If supply frequency increases the opposition also be increased. For this reason, an inductor can totally block the very high-frequency AC.

Induction types

• Self Induction
• Mutual Induction

Inductance unit

• American physicist Joseph Henry  — henry  (unit of either self-inductance or mutual inductance)
• One henry is the value of self-inductance in a closed circuit or coil in which one volt is produced by a variation of the inducing current of one ampere per second.

Inductor  Vs Resistors

• Inductors are used for reducing current in AC circuits without any loss of electrical energy
• When resistors are used, electrical energy is wasted in the form of heat