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Va- VA
- Abbreviation of VoltAmpere, the product of rms voltage and rms current in an electronic circuit. It is the unit of apparent power in the International System of Units (SI).
- Vacancy
- An unfilled lattice site in a crystal structure.
- Vacuum
- A given space filled with gas at pressures below atmospheric pressure.
- Vacuum Engine
- The working principle is similar to the hot air engine, except that this engine draws hot air into the cylinder.
- Valence
- The charge on an ion based on the number of electrons transferred or shared within a specific structure.
- Valence Band
- Highest filled or almost filled band in a semiconductor.
- Valence Bond
- In the valence bond theory, a valence bond is a chemical bond formed by overlap of half-filled atomic orbitals on two different atoms.
- Valence Electrons
- The electrons in the outermost shell of an atom.
- Valve
- In electronics, a valve is a device consisting of two or more metal plates enclosed in an evacuated glass bulb.
- Valve Float
- A high-rpm engine condition in which the valve lifters lose contact with the cam lobes because the valve springs are not strong enough to overcome the momentum of the various valvetrain components.
- Valve Lifter
- The cylindrically shaped component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates.
- Valve Seat
- That part of the valve mechanism upon which the valve face rests to close the port.
- Valve Spring
- The spring which is used to close a valve.
- Valves
- Signifies the total intake and exhaust valves in an internal combustion engine.
- Valve-Spring Retainer
- Holds the valve spring in a state of compression.
- Valvetrain
- The collection of parts that make the valves operate in an internal combustion engine.
- Van Allen Belts
- Radiation belts of high-energy particles trapped in the earth's magnetosphere.
- van der Waals Bond
- A secondary interatomic bond between adjacent molecular dipoles, which may be permanent or induced.
- van der Waals Equation
- An equation for non-ideal gasses that accounts for intermolecular
attraction and the volumes occupied by the gas molecules.
- van der Waals Force
- A force acting between nonbonded atoms or molecules. Includes dipole-dipole, dipole-induced dipole, and London forces.
- van der Waals Radius
- One half the distance between two nonbonded atoms, when attractive and repulsive forces between the atoms are balanced.
- Vanadium
- The principal use for vanadium is as an alloying constituent, particularly in steels where it is introduced as ferrovanadium, an alloy of iron and vanadium.
- Vapour
- A gas whose temperature is below its critical temperature, so that it can be condensed to the liquid or solid state by increase of pressure alone.
- Vapour Pressure
- The partial pressure of a gas in equilibrium with a condensed form (solid or liquid) of the same substance.
- Vapour Trail
- A cloud like streamer or trail often seen behind aircraft flying in clear, cold, humid air.
- Varactor
- A p-n junction diode that is designed to act as a voltage controlled capacitance when it is operated under reverse bias.
- Variable
- A letter that is used to represent a numerical quantity whose value may or may not yet be known.
- Variance
- The square of the difference from the mean for each data value, summed and divided
by one less than the number of values.
- Varnish
- A resin in solution.
- Vault
- An arched brick or stone ceiling or roof.
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