VLF (very-low frequency) (radio frequencies). The range of radio frequencies between three kilohertz (3,000 cycles per second) and 30 kilohertz (30,000 cycles per second). VLF radio waves are used for operations that require the signal to travel great distances.
VNE (never-exceed speed). The maximum speed an aircraft is allowed to attain in any conditions of flight. VNE is marked on the airspeed indicator with a red radial line.
volatile liquid. A liquid that evaporates easily, or readily turns into a vapor. Alcohol and gasoline are both volatile liquids.
volatile memory (computer memory). Memory in a computer in which all data is lost when power to the computer is turned off. Dynamic RAMs (random access memories) store data in the form of charges on capacitors. Memory stored in this manner is volatile.
volatility. The characteristic of a liquid that relates to its ability to vaporize, or change into a gas.
volt (electrical unit). The basic unit of electrical pressure. One volt is the amount of electrical pressure needed to force one ampere of current through a resistance of one ohm. One volt is also the amount of electrical pressure drop that occurs when a current of one ampere produces one watt of power.
voltage amplifier (electronic circuit). An electronic circuit capable of increasing voltage. Voltage amplifiers normally supply an extremely small amount of current.
voltage divider (electrical circuit). An electrical circuit in which a tapped resistor or a series of resistors is installed across a voltage source to provide various output voltages. The sum of the voltage drops across each of the resistances in a voltage divider is the same as the voltage across the entire resistance.
voltage doubler (electrical circuit). An electrical circuit in which alternating current is rectified, and its output is increased to a value of twice its original peak value.
voltage drop. The drop in voltage or electrical pressure caused by current flowing through a resistance. A voltage drop is called an IR (current times resistance) drop.
voltage quadrupler (electrical circuit). An electrical circuit in which alternating current is rectified, and its output is increased to a value four times its original peak value.
voltage regulator (generator or alternator control). A device which holds the output voltage of a generator or alternator constant as its speed changes in normal operation and its load current changes within its rated value.
voltage regulator tube (electron tube). A special gas-filled electron tube. The tube, in series with a resistor, is placed across the output of a DC power supply. The gas in the tube ionizes when a specific voltage is placed across it, and when the gas ionizes, electrons flow through it with very little opposition. The voltage drop across the regulator tube remains constant as the load current changes.