a constant potential difference of 1 volt across
magnetic material and can cause currents to be
the resistance will maintain a current flow of 1
induced in conducting bodies moving relative to
ampere through the resistance.
the magnetized bodies.
MANUAL BUS TRANSFER (MBT)
OHMIC VALUE-- Resistance in ohms.
SWITCH-- Provides selection between normal
and alternate power sources for selected
OHM'S LAW-- The current in an electric circuit is
equipment. This transfer switch is used for
directly proportional to the electromotive force
controllers with low voltage protection that
in the circuit. The most common form of the
requires manual restarting after voltage failure
law is E=IR, where E is the electromotive force
and for electronic power distribution panels.
or voltage across the circuit, I is the current
flowing in the circuit, and R is the resistance of
MEGA-- A prefix meaning one million, also Meg or
the circuit.
M.
P
MHO-- Unit of conductance; the reciprocal of the
ohm.
PARALLAX ERROR-- The error in meter readings
that results when you look at a meter from some
position other than directly in line with the
MICRO-- A prefix meaning one-millionth.
pointer and meter face. A mirror mounted on
the meter face aids in eliminating parallax error.
MILLI-- A prefix meaning one-thousandth.
PARALLEL CIRCUIT-- Two or more electrical
MOVING-VANE METER MOVEMENT-- A meter
devices connected to the same pair of terminals
movement that uses the magnetic repulsion of
so separate currents flow through each;
the like poles created in two iron vanes by
electrons have more than one path to travel
current through a coil of wire; most commonly
from the negative to the positive terminal.
used movement for ac meters.
PERMEABILITY-- The measure of the ability of
MULTIMETER-- A single meter combining the
material to act as a path magnetic lines of force.
PHASE-- The angular relationship between two
alternating currents or voltages when the voltage
N
or current is plotted as a function of time.
When the two are in phase, the angle is zero,
NEGATIVE TEMPERATURE COEFFICIENT-- The
and both reach their peak simultaneously.
temperature coefficient expressing the amount
When out of phase, one will lead or lag the
of reduction in the value of a quantity, such as
other; at the instant when one is at its peak, the
resistance for each degree of increase in
other will not be at peak value and (depending
temperature.
on the phase angle) may differ in polarity as
well as magnitude.
N E U T R A L -- In a normal condition; therefore
neither positive nor negative. A neutral object
PHASE ANGLE-- The number of electrical degrees
has a normal number of elections.
of lead or lag between the voltage and current
waveforms in an ac circuit.
NONTRIP-FREE CIRCUIT BREAKER-- A circuit
breaker that can be held ON during an over
PHASE DIFFERENCE-- The time in electrical
current condition.
degrees by which one wave leads or lags
another.
O
P H O T O E L E C T R I C V O L T A G E -- A voltage
OHM
The unit of electrical resistance. It is
produced by light.
that value of electrical resistance through which
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