Defining a cathode
Defining a cathode
OK, I'm quite confused. And yes, I understand the historical controversy of conventional current flow and that of electron flow.<p>I am wondering why the cathode of a diode or transitors is considered a negative terminal while on a supply battery (standard 12V) the cathode is considered to be the positive terminal. <p>There was a well-written article on current flow in the July '02 issue of Nuts & Volts, by Louis Frenzel that show the workings of a battery but he doesn't mention the terminal names. I am having a problem with the information site, Atomica.com, cause they described a cathode as a positive terminal. Is this correct? If so, why are some electronic devices' terminals considered to be negatively-charged.<p>So, is a negative battery terminal called a cathode or an anode. All the dictionary's that I have read are contradictory, especially American Heritage's.<p>For a battery graphic reference please see valence.com and go to battery education page.<p>
J.Parker
Re: Defining a cathode
Jeeves told me:<p>cathode
1 : the electrode of an electrochemical cell at which reduction occurs: a : the negative terminal of an electrolytic cell b : the positive terminal of a galvanic cell<p>IversonSoftware.com told me:<p>Electrolytic cell, an apparatus in which chemical change is caused to occur through the application of electrical energy.<p>Galvanic cell, an apparatus in which a spontaneous redox reaction is used to convert chemical energy to electrical energy.<p>My interpretation of these definitions is that a galvanic cell is a device that provides electrical energy, whereas an electrolytic cell is a device that accepts electrical energy. Therefore, I assume that the designator of cathode depends on the battery's current state. If the battery is being charged, it is acting as anaelectrolytic cell and the cathode is the negative terminal. Conversly, if the battery is being discharged, it is acting as a galvanic cell and the cathode is therefore the positive terminal.<p>Anyone else have any thoughts?<p>[ September 08, 2002: Message edited by: bobsRAC ]</p>
1 : the electrode of an electrochemical cell at which reduction occurs: a : the negative terminal of an electrolytic cell b : the positive terminal of a galvanic cell<p>IversonSoftware.com told me:<p>Electrolytic cell, an apparatus in which chemical change is caused to occur through the application of electrical energy.<p>Galvanic cell, an apparatus in which a spontaneous redox reaction is used to convert chemical energy to electrical energy.<p>My interpretation of these definitions is that a galvanic cell is a device that provides electrical energy, whereas an electrolytic cell is a device that accepts electrical energy. Therefore, I assume that the designator of cathode depends on the battery's current state. If the battery is being charged, it is acting as anaelectrolytic cell and the cathode is the negative terminal. Conversly, if the battery is being discharged, it is acting as a galvanic cell and the cathode is therefore the positive terminal.<p>Anyone else have any thoughts?<p>[ September 08, 2002: Message edited by: bobsRAC ]</p>
Re: Defining a cathode
I agree with Bobsrac: The cathode is the terminal that emitts electrons internally. It is the negative terminal of a vacuum tube, but the positive terminal of a battery source.
Re: Defining a cathode
Am still confused, but here's some of my researched info.<p>Please note that a 12V battery is considered to be a secondary battery.<p>Add'tl info:<p>Cathode-
An electrode through which current normally leaves the medium of different conductivity. -Int'l Electrotechnical Commission<p>Cathode-
The electrode in an electrochemical cell where reduction takes place.
1). During discharge, the positive electrode of the cell is the cathode.
2). During charge, the situation reverses, and the negative electrode of the cell is the cathode. -Battery Technologies, Inc.<p>Holonyms of the noun cathode -2 senses of cathode <p>Sense 1 cathode --
(a negatively charged electrode that is the source of electrons in an electrical device)<p>PART OF: electrolytic cell -- (a cell containing an electrolyte in which an applied voltage causes a reaction to occur that would not occur otherwise (such as the breakdown of water into hydrogen and oxygen)) <p>PART OF: tube, vacuum tube, thermionic vacuum tube, thermionic tube, electron tube, thermionic valve -- (electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope) <p>PART OF: circuit, electrical circuit, electric circuit -- (an electrical device that provides a path for electrical current to flow) <p>PART OF: electronic equipment -- (equipment that involves the controlled conduction of electrons (especially in a gas or vacuum or semiconductor)) <p>Sense 2 cathode --
the positively charged terminal of a voltaic cell or storage battery that supplies current) <p>PART OF: storage battery, accumulator -- (a voltaic battery that stores electric charge) <p>PART OF: voltaic cell, galvanic cell, primary cell -- (an electric cell that generates an electromotive force by an irreversible conversion of chemical to electrical energy; cannot be recharged) <p>PART OF: voltaic battery, galvanic battery -- (battery consisting of a number of voltaic cells arranged in series or parallel)
__________<p>cathode-
The electrode where reduction occurs in an electrochemical cell. It is the negative electrode in an electrolytic cell, while it is the positive electrode in a galvanic cell.
The current on the cathode is considered a negative current according to international convention; however, in electroanalytical chemistry the cathodic current is often considered positive.-electrochem.cwru.edu/ed/dict.htm
________________________
cathode-
1. A negatively charged electrode, as of a electrolytic cell or storage battery.<p> 2. The positively charged terminal of a primary cell or a storage battery that is supplying current.<p>
[Gk. kathodos, descent]
American Heritage Dictionary<p>___________
Cathode ray n. 1 A stream of electrons emitted by the cathode in a electrical discahrge tube.<p>___________
electrode-
terminal through which electric current passes between metallic and nonmetallic parts of an electric circuit. In most familiar circuits current is carried by metallic conductors, but in some circuits the current passes for some distance through a nonmetallic conductor. For example, in electrolysis current passes through a liquid electrolyte; in a fluorescent lamp current passes through a gas. An electrode is usually in the form of a wire, rod, or plate. It may be made of a metal, e.g., copper, lead, platinum, silver, or zinc, or of a nonmetal, commonly carbon. The electrode through which current passes from the metallic to the nonmetallic conductor is called the anode, and that through which current passes from the nonmetallic to the metallic conductor, the cathode. (Electron flow is in a direction opposite that of conventionally defined current.) In most familiar electric devices, current flows from the terminal at higher electric potential (the positive electrode) to the terminal at lower electric potential (the negative electrode); therefore, the anode is usually the positive electrode and the cathode the negative electrode. In some electric devices, e.g., an electric battery, nonelectric energy is converted to electric energy, causing current to flow within the device from the negative electrode to the positive electrode, so that the anode is the negative electrode and the cathode is the positive electrode. - The Columbia Electronic Encyclopedia Copyright © 1994, 2000, Columbia University Press.
________________<p>Cathode-
Terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. In a battery or other source of direct current, the cathode is the positive terminal. In a passive load it is the negative terminal. In an electron tube, such as a cathode-ray tube, electrons stream off the cathode and travel through the tube toward the anode.
________<p>Anode-
Terminal or electrode from which electrons leave a system. In a battery or other source of direct current, the anode is the negative terminal. In a passive load it is the positive terminal. In an electron tube, electrons from the cathode travel across the tube toward the anode; in an electroplating cell, negative ions are deposited at the anode. -Britannica concise
________<p>Modified Battery Revs Up Hybrid-Electric Vehicles
HowStuffWorks.com<p>A new type of electrolyte for lithium-ion batteries, developed by scientists at Brookhaven National Laboratory, is expected to produce batteries that are less expensive and more environmentally friendly. By raising the capacity of these new boron-based electrolyte batteries, researchers believe they can develop a more efficient power source for hybrid electric vehicles (HEVs). <p>Lithium-ion batteries are lightweight, rechargeable batteries that were developed in the early 1990s. At the core of these batteries is a lithium compound that acts as the anode, the negatively charged terminal where an electric current exits a battery to charge a device. Traditionally, lithium-ion batteries have used toxic-salts as the electrolyte for the chemical fluid that forms the internal, electrical connection between the anode and the cathode -- the cathode being the positively charged terminal where the electrical current returns to the battery.<p>
Ask Jeeves:<p>The cathode is indeed the negative electrode, where reduction occurs, and the
anode the positive electrode, where oxidation takes place. If you (like me)
have had "cation = positive" and "anion = negative" drummed into your head,
you can remember this by remembering that the cathode is where cations go and
the anode is where anions go, and that opposite charges attract.<p>Yer friendly MadSci admin,<p>Dan Berger<p>[ September 09, 2002: Message edited by: Jay ]<p>The chemical equation for electrolysis is:<p>energy (electricity) + 2 H2O -> O2 + 2 H2 . <p>At the cathode (the negative electrode), there is a negative charge created by the battery. This means that there is an electrical pressure to push electrons into the water at this end. At the anode (the positive electrode), there is a positive charge, so that electrode would like to absorb electrons.<p>[ September 09, 2002: Message edited by: Jay ]</p>
An electrode through which current normally leaves the medium of different conductivity. -Int'l Electrotechnical Commission<p>Cathode-
The electrode in an electrochemical cell where reduction takes place.
1). During discharge, the positive electrode of the cell is the cathode.
2). During charge, the situation reverses, and the negative electrode of the cell is the cathode. -Battery Technologies, Inc.<p>Holonyms of the noun cathode -2 senses of cathode <p>Sense 1 cathode --
(a negatively charged electrode that is the source of electrons in an electrical device)<p>PART OF: electrolytic cell -- (a cell containing an electrolyte in which an applied voltage causes a reaction to occur that would not occur otherwise (such as the breakdown of water into hydrogen and oxygen)) <p>PART OF: tube, vacuum tube, thermionic vacuum tube, thermionic tube, electron tube, thermionic valve -- (electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope) <p>PART OF: circuit, electrical circuit, electric circuit -- (an electrical device that provides a path for electrical current to flow) <p>PART OF: electronic equipment -- (equipment that involves the controlled conduction of electrons (especially in a gas or vacuum or semiconductor)) <p>Sense 2 cathode --
the positively charged terminal of a voltaic cell or storage battery that supplies current) <p>PART OF: storage battery, accumulator -- (a voltaic battery that stores electric charge) <p>PART OF: voltaic cell, galvanic cell, primary cell -- (an electric cell that generates an electromotive force by an irreversible conversion of chemical to electrical energy; cannot be recharged) <p>PART OF: voltaic battery, galvanic battery -- (battery consisting of a number of voltaic cells arranged in series or parallel)
__________<p>cathode-
The electrode where reduction occurs in an electrochemical cell. It is the negative electrode in an electrolytic cell, while it is the positive electrode in a galvanic cell.
The current on the cathode is considered a negative current according to international convention; however, in electroanalytical chemistry the cathodic current is often considered positive.-electrochem.cwru.edu/ed/dict.htm
________________________
cathode-
1. A negatively charged electrode, as of a electrolytic cell or storage battery.<p> 2. The positively charged terminal of a primary cell or a storage battery that is supplying current.<p>
[Gk. kathodos, descent]
American Heritage Dictionary<p>___________
Cathode ray n. 1 A stream of electrons emitted by the cathode in a electrical discahrge tube.<p>___________
electrode-
terminal through which electric current passes between metallic and nonmetallic parts of an electric circuit. In most familiar circuits current is carried by metallic conductors, but in some circuits the current passes for some distance through a nonmetallic conductor. For example, in electrolysis current passes through a liquid electrolyte; in a fluorescent lamp current passes through a gas. An electrode is usually in the form of a wire, rod, or plate. It may be made of a metal, e.g., copper, lead, platinum, silver, or zinc, or of a nonmetal, commonly carbon. The electrode through which current passes from the metallic to the nonmetallic conductor is called the anode, and that through which current passes from the nonmetallic to the metallic conductor, the cathode. (Electron flow is in a direction opposite that of conventionally defined current.) In most familiar electric devices, current flows from the terminal at higher electric potential (the positive electrode) to the terminal at lower electric potential (the negative electrode); therefore, the anode is usually the positive electrode and the cathode the negative electrode. In some electric devices, e.g., an electric battery, nonelectric energy is converted to electric energy, causing current to flow within the device from the negative electrode to the positive electrode, so that the anode is the negative electrode and the cathode is the positive electrode. - The Columbia Electronic Encyclopedia Copyright © 1994, 2000, Columbia University Press.
________________<p>Cathode-
Terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. In a battery or other source of direct current, the cathode is the positive terminal. In a passive load it is the negative terminal. In an electron tube, such as a cathode-ray tube, electrons stream off the cathode and travel through the tube toward the anode.
________<p>Anode-
Terminal or electrode from which electrons leave a system. In a battery or other source of direct current, the anode is the negative terminal. In a passive load it is the positive terminal. In an electron tube, electrons from the cathode travel across the tube toward the anode; in an electroplating cell, negative ions are deposited at the anode. -Britannica concise
________<p>Modified Battery Revs Up Hybrid-Electric Vehicles
HowStuffWorks.com<p>A new type of electrolyte for lithium-ion batteries, developed by scientists at Brookhaven National Laboratory, is expected to produce batteries that are less expensive and more environmentally friendly. By raising the capacity of these new boron-based electrolyte batteries, researchers believe they can develop a more efficient power source for hybrid electric vehicles (HEVs). <p>Lithium-ion batteries are lightweight, rechargeable batteries that were developed in the early 1990s. At the core of these batteries is a lithium compound that acts as the anode, the negatively charged terminal where an electric current exits a battery to charge a device. Traditionally, lithium-ion batteries have used toxic-salts as the electrolyte for the chemical fluid that forms the internal, electrical connection between the anode and the cathode -- the cathode being the positively charged terminal where the electrical current returns to the battery.<p>
Ask Jeeves:<p>The cathode is indeed the negative electrode, where reduction occurs, and the
anode the positive electrode, where oxidation takes place. If you (like me)
have had "cation = positive" and "anion = negative" drummed into your head,
you can remember this by remembering that the cathode is where cations go and
the anode is where anions go, and that opposite charges attract.<p>Yer friendly MadSci admin,<p>Dan Berger<p>[ September 09, 2002: Message edited by: Jay ]<p>The chemical equation for electrolysis is:<p>energy (electricity) + 2 H2O -> O2 + 2 H2 . <p>At the cathode (the negative electrode), there is a negative charge created by the battery. This means that there is an electrical pressure to push electrons into the water at this end. At the anode (the positive electrode), there is a positive charge, so that electrode would like to absorb electrons.<p>[ September 09, 2002: Message edited by: Jay ]</p>
J.Parker
Re: Defining a cathode
Jay, you say that a 12V battery is considered to be a secondary battery.
Well, that is true only if it is composed of secondary, i.e. rechargeable, cells, such as that in your automobile.
The ubiquitous PP3 nine-volt battery (the voltage is totally irrelevant) is a primary battery because it is made up of six 1.5V primary (non- rechargeable) cells. And so were the 90V, and more, batteries which we used to be able to buy for the B+ supplies in portable (tube) radios.
I can't imagine who told you what you obviously believe to be true, but they are confused.
Regards,
David
Well, that is true only if it is composed of secondary, i.e. rechargeable, cells, such as that in your automobile.
The ubiquitous PP3 nine-volt battery (the voltage is totally irrelevant) is a primary battery because it is made up of six 1.5V primary (non- rechargeable) cells. And so were the 90V, and more, batteries which we used to be able to buy for the B+ supplies in portable (tube) radios.
I can't imagine who told you what you obviously believe to be true, but they are confused.
Regards,
David
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Chris Smith
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Re: Defining a cathode
Every thing is a perspective view.<p>The pos returns through the neg lead, or makes a loop?<p> It attracts the pos, absorbs it, or how ever you want to look at it?<p>Is it push or pull? <p>Doesn't matter, assign one and go with the logic, That's why there are two assigned theories. <p>As long as you assign one, and stick to it all the laws will cooperate.
Re: Defining a cathode
Isn't that conventional flow vs electron flow??
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Chris Smith
- Posts: 4325
- Joined: Tue Dec 04, 2001 1:01 am
- Location: Bieber Ca.
Re: Defining a cathode
Exactly, and they both work as long as you dont mix them.
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