PLATE MODULATION.--See Modulation, Plate.
PLATE VOLTAGE.--See Foliage, Plate.
POLES, BATTERY.--The positive and negative terminals of the elements of a battery. On a storage battery these poles are marked + and - respectively.
POLES, MAGNETIC.--The ends of a magnet.
POSITIVE ELECTRICITY.--See Electricity, Positive.
POTENTIAL DIFFERENCE.--The electric pressure between two charged conductors or surfaces.
POTENTIOMETER.--A variable resistance used for subdividing the voltage of a current. A voltage divider.
POWER TRANSFORMER.--See Transformer, Power.
POWER TUBE.--See Generator Tube.
PRIMARY BATTERY.--See Battery, Primary.