Midterms (Chapter 14. Part 2) Flashcards
(14 cards)
the SI unit of magnetomotive force (mmf)
Ampere Turn
the SI unit of field intensity, H.
Ampere-Turns/meter
a graph showing how the flux density, B, in
teslas, increases with the field intensity, H, in ampere-turns/meter.
B-H magnetization curve
law for determining
the amount of induced voltage in a
conductor.
Faraday’s Law
the amount of mmf per unit length. The units
for fi eld intensity are At/m and oersted
Field Intensity
the minimum amount of relay coil current required to keep a relay energized or operating.
Holding current
means lagging behind. With respect to the magnetic flux in an iron core of an
electromagnet, the fl ux lags behind the increases and decreases in magnetizing force.
Hysteresis
if a coil is grasped with the fingers of the left hand curled around the coil in the direction of
electron flow, the thumb points to the
north pole of the coil.
Left-hand Rule
the direction of the induced current in
a conductor must be such that its own magnetic field will oppose the action that produced the induced current
Lenz’s Law
a measure of the strength of a
magnetic field based on the amount
of current fl owing in the turns of a
coil. The units of mmf are the ampere
turn (A? t) and the gilbert (Gb).
Magnetomotive Force
a motion that results from the net force of two magnetic fields that can aid or cancel each other. The direction of the resultant
force is always from a stronger fi eld
to a weaker fi eld.
Motor Action
the minimum amount of relay coil current necessary to energize or operate a relay.
Pickup Current
the point in a magnetic material, such as an iron core, where further increases in fi eld intensity produce no further increases in flux
density.
Saturation
