The document explains the behavior of inductors in electrical circuits, emphasizing how they build and collapse magnetic fields in response to current flow and changes. It describes inductive reactance as the opposition to changes in current, especially under alternating current (AC) conditions where the frequency affects the level of reactance. At high frequencies, inductors significantly impede current flow, creating a balance where the current appears to stop altogether.

2. Original inductor

3. Current begins to flow

4. Magnetic field begins to form

5. Magnetic field builds

6. Magnetic field at maximum strength

7. Inductance
• As current flows through an inductor, a
magnetic field builds up.
• Moving charges (current) induces a
magnetic field.

8. Current stops

9. Magnetic field collapses, causing
current to temporarily continue

10. Inductive Reactance
• When current drops or stops, energy is
returned to the circuit from the magnetic
field
• Returning energy causes current to
continue to flow in the same direction as it
was.
• This induced current opposes changes in
current.
• Opposition to changes in current is called
inductive reactance.

11. Inductors and AC current

12. AC current reverses direction

13. Collapsing magnetic field induces
opposing current

14. Magnetic field now builds in
opposite polarity

15. Inductive Reactance and AC
• With AC, inductors alternate between
building and collapsing magnetic fields.
• The faster the current changes direction
(the higher the frequency), the more
current changes are opposed because the
magnetic field has not had time to
collapse and is still strong.
• The higher the frequency, the greater the
inductive reactance.

16. Inductor at high frequency AC

17. Inductive Reactance and AC
• The higher the frequency, the greater the
inductive reactance.
• At high frequency, the current through an
inductor is like a tug of war between
evenly matched teams. Current
essentially stops.