11. When the current increases, the magnetic field expands; and when the current decreases, the magnetic
12. The induced voltage emf in any circuit is always in a direction to oppose the effect that produced it.
The unit of measurement of inductance is the HENRY, and its associated symbol is an "h." An inductor has
an inductance of 1 henry if 1 volt is induced in the inductor when the current through the inductor is
changing at the rate of 1 ampere per second. This relationship may be stated mathematically as:
where E = the induced emf in volts
L = the inductance in henrys
I = the change in current in amperes
t = the change in time in seconds
NOTE: The symbol Δ (Delta) means "a change in..." Remember, it is the change in
current, not the current itself, that is opposed by the inductor
The henry is a large unit of inductance. The more common units employed with inductors
are millihenry (mh) and the microhenry (h).
Q. What is the unit of measurement of inductance and its associated symbol?
The inductance of a coil depends on four factors:
(1) the number of turns of wire in the coil (N),
(2) the cross-sectional area of the coil (A),
(3) the length of the coil (1), and
(4) the permeability of the coils core ().
The formula expressing is relationship is: