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plasma length • plated magnetic wire 537
plasma length See DEBYE LENGTH.
plasma oscillation In a plasma, a form of electricfield
oscillation of the rapidly moving electrons.
plasma torch A torch, used for such high-heat applications
as melting metal, in which a gas is
heated by electricity to the high temperature at
which it becomes a plasma.
plasmatron A form of amplifier tube sometimes
used at ultra-high and microwave frequencies. It
is similar to a thyratron. An inert gas is excited
until it becomes a plasma, producing amplification
under certain operating conditions.
Plastacele See CELLULOSE ACETATE.
plastic A synthetic material usually made from
various organic compounds through polymerization
(see POLYMERIZE). Plastics can be molded
into solid shapes and are available as films. Examples:
celluloid, cellulose acetate, cellulose nitrate,
polyethylene, and polystyrene. Also see
THERMOPLASTIC MATERIAL and THERMOSET-
TING MATERIAL.
plastic-film capacitor A capacitor made using
polyester, polyethylene, or polystyrene. The
method of manufacture is similar to that for paper
capacitors when the plastic is flexible. Stacking
methods can be used if the plastic is more
rigid. The geometries can vary, and these capacitors
are therefore found in several different
shapes. Capacitance values for plastic-film units
range from about 50 pF to several tens of microfarads.
Most often they are in the range of 0.001 µF
to 10 µF. Plastic-film capacitors are employed in
audio equipment, and also in wireless transmitters
and receivers. The efficiency is good, although
not as high as that for mica-dielectric
units. Compare CERAMIC CAPACITOR, ELEC-
TROLYTIC CAPACITOR, MICA CAPACITOR, PA-
PER CAPACITOR, TANTALUM CAPACITOR.
plasticizer A substance added to a plastic to make
it softer or more flexible.
plastic-leaded chip carrier Abbreviated PLCC. A
surface-mounted package for an integrated circuit.
It is small in size and has high electrical and
mechanical reliability.
plate 1. The anode of an electron tube. 2. One of
the electrodes of a primary or secondary battery
cell. 3. One of the electrodes of a capacitor.
plateau In a response curve, a region in which an
increase in the independent variable produces no
further change in the dependent variable. Example:
the saturation region in a common-base
transistor collector-current curve.
plate blocking capacitor A capacitor connected
between the plate of an electron tube and the
plate tank. It allows the direct-current supply
voltage to be applied directly to the plate without
it passing through the tank coil, while at the
same time preventing the tank coil from shortcircuiting
the plate power supply. The capacitor
freely transmits alternating-current signal energy
to the tank.
y
y = f (x)
plateau
Plateau
plate capacitance See PLATE-CATHODE CAPACI-
TANCE.
plate-cathode capacitance Symbol, C PK . Unit, pF.
The internal capacitance between the plate and
cathode of an electron tube. Also called OUTPUT
CAPACITANCE.
plate characteristic For an electron tube, the family
of plate current-vs-plate voltage curves for various
grid-bias voltages.
plate circuit The external circuit associated with
the plate of an electron tube.
plate-circuit relay A direct-current relay operated
in series with the plate of an electron tube.
plate conductance Symbol, g P . Unit, siemens.
Conductance of the internal plate circuit of an
electron tube. The value of static g P is equal to the
plate current divided by the plate voltage (I P /E P ).
The value of dynamic g P is equal to the derivative
of the static g P : d IP /d EP . Plate conductance is the
reciprocal of PLATE RESISTANCE.
plate current Symbol, I P . Direct current flowing in
the plate circuit of an electron tube.
plate-current shift A change in the plate current
of a radio-frequency power amplifier during amplitude
modulation. The action discloses faulty
operation because the average plate current
should remain constant during modulation.
plate dissipation Abbreviation, PD. Unit, watt.
Power expended in the plate of an electron tube.
For an unloaded tube, PD = E P I P , where E P is the
direct-current (dc) plate voltage in volts, and I P is
the dc plate current in amperes. For a loaded
tube, PD = P o – P i , where P o is the alternatingcurrent
(ac) power output of an amplifier or
oscillator in which the tube operates, and P i is the
dc plate power input.
plated magnetic wire A wire with a ferromagnetic
outer coating on a core that is not magnetic.
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