Resistance and Induction
Name: Venkatesh K.
Just as I say that resistance is caused by the
obstruction to the motion of electrons in a resistor, what is the
physical interpretation of inductance (i.e. why does an inductor oppose
any sudden change in current through it)?
Inductance is a magnetic property, actually a combination of magnetic and
electric properties. Current flowing through a wire causes a magnetic field
to circle around the wire. A CHANGING magnetic field creates an electric
field around itself. With a straight wire, this has no significant effect.
If the wire is wrapped in a coil, however, inductance occurs. When current
changes, magnetic field changes. The changing magnetic field through the
center of the coil causes electric field that opposes the CHANGE of the
current. A voltage is produced across the coil pushing opposite the change.
An inductor will allow any size current to flow, so long as the current
doesn't change. A slow change has very little effect. A fast change
produces a quick change of the magnetic field, which produces a large
voltage to oppose the change.
Scientists know that induction does happen. We know it is because changing
magnetic fields produce electric fields. We do not, however, know WHY
changing magnetic fields produce electric fields.
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012