# volt +

#### (unit of measurement of electromotive force, or pressure, in an electrical circuit, or 'push', named for Alessandro Volta (1745-1827) renowned for his pioneering work in electricity)

voltage cutoff
The electrode voltage that reduces the anode current, beam current, or some other electron-tube or transistor characteristic to a specified low value.
voltage depression
An effect in which the peak voltage of a battery drops more quickly than normal as it is used, even though the total power remains almost the same; often caused by repeated overcharging of the battery.
voltage divider
1. A unit of electric measurement equal to the product of a volt and an ampere that for direct current constitutes a measure of power equivalent to a watt.
2. A tapped resistor, adjustable resistor, potentiometer, or a series arrangement of two or more fixed resistors connected across a voltage source.

A desired fraction of the total voltage is obtained from the intermediate tap, movable contact, or resistor junction.

voltage doubler, doiubler
1. A rectifier circuit that gives approximately double the output voltage of a conventional half-wave vacuum-tube rectifier by charging a capacitor during the normally wasted half-cycle and discharging it in a series with the output voltage during the next half-cycle.
2. An electric circuit for rectifying alternating current in which two rectifiers give double the output voltage available using a single rectifier.
voltage drop
1. The voltage difference between any two specific points in a circuit.
2. The voltage developed across a component or conductor by the flow of current through the resistance or impedance of that component or conductor.
3. The decline in voltage in an electrical circuit because of the resistance in the conducting line.

This is why longer electrical runs in a building require thicker gauge wire and why AC power is transmitted over high-voltage lines.

Higher current requires thicker and more expensive wires, but higher voltage does not. The high-voltage lines are reduced by transformers near the end of the line.

voltage feed
Excitation of a transmitting antenna by applying voltage at a point of maximum potential; at a voltage loop or antinode.
voltage feedback
1. A feedback configuration where a portion of the output voltage is fed back to the input of an amplifier.
2. Feedback in which the voltage drop across part of a load impedance acts in a series with the input signal voltage.
voltage follower
1. An amplifier used after an oscillator or other critical stage to isolate it from the effects of load impedance variations in subsequent stages. Also known as buffer; buffer stage.
2. An analog device that is typically used for impedance matching and signal isolation; for example, a sound card typically uses buffer amps at most of its input and output ports.
3. An operational amplifier that has no feedback components but has a direct feedback connection from the output to the inverting input to give unity gain so the output voltage follows the non-inverting input voltage.

A voltage follower has a very high input impedance and a very low output impedance.

voltage gain
The difference between the output signal voltage level in decibels and the input signal voltage level in decibels.

This value is equal to twenty times the common logarithm of the ratio of the output voltage to the input voltage.

The voltage gain is equal to the amplification factor of the tube or transistor only for a matched load.

voltage generator
A two-terminal circuit element in which the terminal voltage is independent of the current through the element or component.
1. The voltage per unit length along a resistor or other conductive path.
2. The electric field in a region, defined as the potential difference between two points divided by the distance between them.
voltage jump
An abrupt change or discontinuity in tube voltage drop during operation of a glow-discharge tube.
voltage law, Kirchhoff's voltage law
1. The law that at each instant of time the algebraic sum of the voltage rises around a closed loop in a network is equal to the algebraic sum of the voltage drops, both being taken in the same direction around the loop.
2. The statement that the sum of all currents flowing into a node is zero; conversely, the sum of all currents leaving a node must be zero.

Gustav Kirchhoff (184-1887) was a German physicist noted for his formulation of laws related to the conduction of electricity. He also made major contributions in the study of spectroscopy and advanced research into blackbody radiation (emission of radiant energy which would take place from a blackbody at a fixed temperature).

A blackbody is the theoretical surface that absorbs all radiant energy that falls on it, and radiates electromagnetic energy at all frequencies, from radio waves to gamma rays. Because all visible light falling on such a surface is absorbed without reflection, the surface will appear black as long as its temperature is such that its emission peak is not in the visible portion of the spectrum.

voltage loop
An antinode at which voltage is at a maximum.
voltage multiplier
1. A rectifier circuit capable of supplying a direct-current output voltage that is two or more times the peak value of the alternating-current voltage.
2. An electronic circuit that converts AC to DC and multiplies the source voltage.

It consists of capacitor/diode pairs, the capacitor stores the source voltage like a charge pump, and the diode rectifies it.

The output voltage is roughly the input voltage times the number of capacitor/diode pairs; for example, a voltage doubler uses two capacitor/diode pairs while a voltage tripler uses three pairs.

A cross reference of word units that are related, directly and/or indirectly, with "electricity": electro-; galvano-; hodo-; ion-; piezo-; -tron; biomechatronics, info; mechatronics, info.