Inductors

• Any wire carrying a current is surrounded by a magnetic field; winding the wire into a coil strengthens this field
• When the current through a coil changes the magnetic field resists the change; this resistance to change is called inductance
• The unit of inductance is the Henry (H) but as this is a large unit the milli– and micro–Henry (mH, μH) are more commonly used
• In electronic circuits, inductors are mainly used where the current is alternating – such as in audio frequency or radio frequency circuits
• However, the resistance to change of the magnetic field will also affect a direct current (i.e. non-alternating) circuit during the switch-on phase: if an inductor is connected to a DC power supply, the sudden increase of current in the inductor is initially resisted, but when the current becomes stable, the inductor no longer resists the current

Course Guide Topics

1. Inductor (Coil)
2. Inductors
3. Construction / Characteristics
4. Inductive Reactance