Crossword clues for cathode
cathode
Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Cathode \Cath"ode\, n. [Gr. ? descent; ? down + ? way.]
(Physics)
The part of a voltaic battery by which the electric current
leaves substances through which it passes, or the surface at
which the electric current passes out of the electrolyte; the
negative pole; -- opposed to anode.
--Faraday.
Cathode ray (Phys.), a kind of ray generated at the cathode in a vacuum tube, by the electrical discharge.
Douglas Harper's Etymology Dictionary
1834, from Latinized form of Greek kathodos "a way down," from kata- "down" (see cata-) + hodos "way" (see cede). Proposed by the Rev. William Whewell (1794-1866), English polymath, and published by English chemist and physicist Michael Faraday (1791-1867). So called from the path the electric current was supposed to take. Related: Cathodic; cathodal. Cathode ray first attested 1880, but the phenomenon known from 1859; cathode ray tube is from 1905.
Wiktionary
n. 1 (context electricity English) An electrode, of a cell or other electrically polarized device, through which a positive current of electricity flows outwards (and thus, electrons flow inwards). It usually, but not always, has a positive voltage. 2 (context chemistry by extension English) The electrode at which chemical reduction of cations takes place, usually resulting in the deposition of metal onto the electrode. 3 (context electronics English) The electrode from which electrons are emitted into a http://en.wikipedia.org/wiki/vacuum%20tube or http://en.wikipedia.org/wiki/gas-filled%20tube. 4 (context electronics English) That electrode of a semiconductor device which is connected to the n-type material of a p-n junction.
WordNet
Wikipedia
- A cathode is the electrode from which a conventional current leaves a polarized electrical device. (This definition can be recalled by using the mnemonic CCD for cathode current departs.) A conventional current describes the direction in which positive electronic charges move. Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode.
Cathode polarity with respect to the anode can be positive or negative; it depends on how the device operates. Although positively charged cations always move towards the cathode (hence their name) and negatively charged anions move away from it, cathode polarity depends on the device type, and can even vary according to the operating mode. In a device which takes energy (such as recharging a battery), the cathode is negative, and in a device which provides energy (such as discharging a battery), the cathode is positive:
- In a discharging battery or a galvanic cell, the cathode is the positive terminal since that is where the current flows out of the device (see drawing). This outward current is carried internally by positive ions moving from the electrolyte to the positive cathode (chemical energy is responsible for this "uphill" motion). It is continued externally by electrons moving inwards, this negative charge moving inwards constituting positive current flowing outwards. For example, the Daniell galvanic cell's copper electrode is the positive terminal and the cathode.
- In a recharging battery, or an electrolytic cell performing electrolysis, the cathode is the negative terminal, from which current exits the device and returns to the external generator. For example, reversing the current direction in a Daniell galvanic cell would produce an electrolytic cell, where the copper electrode is the positive terminal and the anode.
- In a diode, the cathode is the negative terminal at the pointed end of the arrow symbol, where current flows out of the device. Note: electrode naming for diodes is always based on the direction of the forward current (that of the arrow, in which the current flows "most easily"), even for types such as Zener diodes or solar cells where the current of interest is the reverse current.
- In vacuum tubes (including cathode ray tubes) it is the negative terminal where electrons enter the device from the external circuit and proceed into the tube's near vacuum, constituting a positive current flowing out of the device.
An electrode through which current flows the other way (into the device) is termed an anode.
Usage examples of "cathode".
Curious bluish jolts of light were emitted undependably from its cathodes.
A set of flat color cathodes arranged on the end wall to resemble a stained-glass window added a certain ecclesiastical air.
Then the cathode ray tube lit up and the slowly revolving timebase drew the picture I had seen so often before.
We must have every foot of space on board packed with extra cathode plates for the geodyne generators.
He contrived to use up the last scrap of cathode plate and the last drop of rocket fuel, in landing here.
The very cathode plates are warped, so that they can never be tuned again.
Just one more landing first, at some out-station, to get food and cathode plates.
Tolentino threw a few electrical switches and the cathode tube monitor of the fluoroscopy unit gave off a light-gray glow.
The cold green, amber and red of the electronics was punctuated by the occasional small patch of cathode blue.
She led the way to a computer terminal-a keyboard with a cathode ray screen above it-and sat down.
They had discovered the X ray, the cathode ray, the electron, and radioactivity, invented the ohm, the watt, the Kelvin, the joule, the amp, and the little erg.
And that tube burnt him, nuked him, its cathodes crackling like cancer.
What Crookes himself thought about these discoveries in the realm of the cathode rays we may judge from the title, 'Radiant Matter', or 'The Fourth State of Matter', which he gave to his first publication about them.
That had been preceded by the discovery of radio waves and cathode rays, and it was to be rapidly followed by the discovery of alpha rays, beta rays, and gamma rays.
The ammonium ion, once the electric current is run through, is attracted to the cathode, which-is in the spoon.