- An inductor opposes changes in current by storing energy in a magnetic field. It consists of a coil of wire and its ability to store energy is called inductance. - Inductance depends on the number of turns in the coil, the diameter of the coil, and the length of the coil. It is measured in henrys. - For inductors in series, the total inductance is the sum of the individual inductances. For inductors in parallel, the total inductance is calculated using the individual inductances and mutual inductance. - Mutual inductance describes the interaction between coils and is considered when coils are in series or parallel. It affects the net inductance based on whether the

2. Inductor
 OPPOSE THE FLOW OF AC BY temporarily
storing some of the electrical energy as
a magnetic field.
 Consist of wire coils.

3. Inductance
 The ability of
the wire coil or
loop to store
energy.
 abbreviated
by the letter L

4. Inductance
 is directly proportional to the number of
turns of wire.
 is also directly proportional to the diameter
of the coil.
 the longer the coil, the less the inductance
𝛍o 𝛍r AN2
𝓵
L =
A = cross sectional area
N = no. of turns
𝓵 = length of coil

5. Unit of Inductance
 henry, abbreviated H,
 represents a potential difference of one
volt across an inductor within which the
current is increasing or decreasing at one
ampere per second.

6. Inductor in series
Without interaction
L = L1 + L2 + L3

7. Inductor in Parallel
L L1 L2 L3
1 1 1 1
= + +

8. Coefficient of coupling
 specified by the letter k, is a number
ranging from 0 (no coupling) to 1 (maximum
possible coupling).
 Two coils that are separated by a sheet of
solid iron would have essentially k = 0
 two coils wound on the same form, one
right over the other, would have practically
k = 1.

9. Mutual inductance
 is specified by the letter M
 is expressed in the same units as
inductance:

10. Effects of mutual
inductance
 When two inductors are connected in
series, and there is reinforcing/aiding
mutual inductance between them.

11. Effects of mutual
inductance
 When two inductors are connected in
series, and there is opposing mutual
inductance between them.

12. Effects of mutual
inductance
 When two inductors are connected in
parallel, and there is reinforcing/aiding
mutual inductance between them.
L1L2 - M2
L1 + L2 - 2M
L =

13. Effects of mutual
inductance
 When two inductors are connected in
parallel, and there is opposing mutual
inductance between them.
L1L2 - M2
L1 + L2 + 2M
L =

14. Energy stored in
the inductor
I2L
2
W = Joules

15. Example 1
a. Find L if L1 and L2 are reinforcing.
b. Find L if L1 and L2 are opposing.

16. Example 2
There are two coils with values L1 = 835 μH and
L2 = 2.44 mH. They are connected in series so
that their coefficient of coupling is 0.922,
acting so that the coils oppose each other.
What is the net inductance of the pair?