query: where do electrons flow in a galvanic cell

pos: Galvanic cell bridge zinc ions leave and anions enter the zinc half-cell. In the copper half-cell, the copper ions plate onto the copper electrode (reduction), taking up electrons that leave the external conductor. Since the Cu ions (cations) plate onto the copper electrode, the latter is called the cathode. Correspondingly the zinc electrode is the anode. The electrochemical reaction is: In addition, electrons flow through the external conductor, which is the primary application of the galvanic cell. As discussed under #Cell voltage, the emf of the cell is the difference of the half-cell potentials, a measure of the relative ease of dissolution

neg: Electrochemistry The two electrodes must be electrically connected to each other, allowing for a flow of electrons that leave the metal of the anode and flow through this connection to the ions at the surface of the cathode. This flow of electrons is an electric current that can be used to do work, such as turn a motor or power a light. A galvanic cell whose electrodes are zinc and copper submerged in zinc sulfate and copper sulfate, respectively, is known as a Daniell cell. Half reactions for a Daniell cell are these: In this example, the anode is the zinc

neg: Electrolytic cell reaction which would not occur spontaneously otherwise. A galvanic cell can be considered an electrolytic cell acting in reverse. While electrolytic cells convert electrical energy into chemical energy, galvanic cells convert chemical energy into electrical energy. Galvanic cells are often used in batteries. Michael Faraday defined the cathode of a cell as the electrode to which cations (positively charged ions, like silver ions Ag) flow within the cell, to be reduced by reacting with electrons (negatively charged) from that electrode. Likewise he defined the anode as the electrode to which anions (negatively charged ions, like chloride ions Cl) flow within

neg: Cathode note the cathode has a 'c', as does 'reduction'. Hence, reduction at the cathode. Perhaps most useful would be to remember cathode corresponds to cation (acceptor) and anode corresponds to anion (donor). The cathode can be negative like when the cell is electrolytic (where electrical energy provided to the cell is being used for decomposing chemical compounds); or positive as when the cell is galvanic (where chemical reactions are used for generating electrical energy). The cathode supplies electrons to the positively charged cations which flow to it from the electrolyte (even if the cell is galvanic, i.e., when the cathode

neg: Cathode is positive and therefore would be expected to repel the positively charged cations; this is due to electrode potential relative to the electrolyte solution being different for the anode and cathode metal/electrolyte systems in a galvanic cell). The cathodic current, in electrochemistry, is the flow of electrons from the cathode interface to a species in solution. The anodic current is the flow of electrons into the anode from a species in solution. In an electrolytic cell, the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or

neg: Anode galvanic cell, the anode is the negative electrode from which electrons flow out towards the external part of the circuit. Internally the positively charged cations are flowing away from the anode (even though it is negative and therefore would be expected to attract them, this is due to electrode potential relative to the electrolyte solution being different for the anode and cathode metal/electrolyte systems); but, external to the cell in the circuit, electrons are being pushed out through the negative contact and thus through the circuit by the voltage potential as would be expected. Note: in a galvanic cell, contrary

neg: Galvanic cell one half-cell is composed of metal A, and the electrode of the other half-cell is composed of metal B; the redox reactions for the two separate half-cells are thus: The overall balanced reaction is In other words, the metal atoms of one half-cell are oxidized while the metal cations of the other half-cell are reduced. By separating the metals in two half-cells, their reaction can be controlled in a way that forces transfer of electrons through the external circuit where they can do useful work. By definition: Galvanic cells, by their nature, produce direct current. The Weston cell has an

neg: Cathode device which absorbs energy of charge (such as recharging a battery), the cathode is negative (electrons flow out of the cathode, and charge flows into it), and in a device which provides energy (such as battery in use), the cathode is positive (electrons flow into it and charge flows out): A battery or galvanic cell in use has a cathode that is the positive terminal since that is where the current flows out of the device. This outward current is carried internally by positive ions moving from the electrolyte to the positive cathode (chemical energy is responsible for this "uphill"

neg: Cathode motion). It is continued externally by electrons moving into the battery which constitutes positive current flowing outwards. For example, the Daniell galvanic cell's copper electrode is the positive terminal and the cathode. A battery that is recharging or an electrolytic cell performing electrolysis has its cathode as the negative terminal, from which current exits the device and returns to the external generator as charge enters the battery/ cell. For example, reversing the current direction in a Daniell galvanic cell converts it into an electrolytic cell where the copper electrode is the positive terminal and also the anode. In a diode,

neg: Anode Anode An anode is an electrode through which the conventional current enters into a polarized electrical device. This contrasts with a cathode, an electrode through which conventional current leaves an electrical device. A common mnemonic is ACID for "anode current into device". The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow out the anode into the outside circuit. In a galvanic cell, the anode is the electrode at which the oxidation reaction occurs. An anode is also the wire or plate having excess

neg: Automotive battery switching the main automotive voltages. Batteries are typically made of six galvanic cells in a series circuit. Each cell provides 2.1 volts for a total of 12.6 volts at full charge. Each cell of a lead storage battery consists of alternate plates of lead (cathode) and lead coated with lead dioxide (anode) immersed in an electrolyte of sulfuric acid solution. The actual standard cell potential is obtained from the standard reduction potentials. This causes a chemical reaction that releases electrons, allowing them to flow through conductors to produce electricity. As the battery discharges, the acid of the electrolyte reacts with

neg: Cathode pure metal from metal ions. When discussing the relative reducing power of two redox agents, the couple for generating the more reducing species is said to be more "cathodic" with respect to the more easily reduced reagent. In a galvanic cell, the cathode is where the positive pole is connected to allow the circuit to be completed: as the anode of the galvanic cell gives off electrons, they return from the circuit into the cell through the cathode. When metal ions are reduced from ionic solution, they form a pure metal surface on the cathode. Items to be plated with

neg: Galvanic cell dioxide, both immersed in sulfuric acid. Large battery rooms, for instance in a telephone exchange providing central office power to user's telephones, may have cells connected in both series and parallel. The voltage (electromotive force "E") produced by a galvanic cell can be estimated from the standard Gibbs free energy change in the electrochemical reaction according to formula_1 where "ν" is the number of electrons transferred in the balanced half reactions, and "F" is Faraday's constant. However, it can be determined more conveniently by the use of a standard potential table for the two half cells involved. The first step

neg: Galvani potential another metal-metal interface, as in the following schematic of a galvanic cell: where: Instead, the measured cell potential can be written as: where: From the above equation, two metals in electronic contact (i.e., under electronic equilibrium) must have the same electrode potential. Also, the electrochemical potentials of the electrons within the two metals will be the same. However, their Galvani potentials will be different (unless the metals are identical). Moreover, if define formula_6, the "electric potential" (or the "electromotive potential in" [6]), as which is effectively negative of the reduced electrochemical potential of electrons given in units of volts. It

neg: Galvanic anode some cathodic (reduction). Electrons flow from the anodic areas into the electrolyte as the metal corrodes. Conversely, as electrons flow from the electrolyte to the cathodic areas the rate of corrosion is reduced. (The flow of electrons is in the opposite direction of the flow of electric current). As the metal continues to corrode, the local potentials on the surface of the metal will change and the anodic and cathodic areas will change and move. As a result, in ferrous metals, a general covering of rust is formed over the whole surface, which will eventually consume all the metal. This

neg: Galvanic cell difference of the reactants and products, denoted as Δ"G". In the Daniell cell, most of the electrical energy of Δ"G" = -213 kJ/mol can be attributed to the -207 kJ/mol difference between Zn and Cu lattice cohesive energies. A half-cell contains a metal in two oxidation states. Inside an isolated half-cell, there is an oxidation-reduction (redox) reaction that is in chemical equilibrium, a condition written symbolically as follows (here, "M" represents a metal cation, an atom that has a charge imbalance due to the loss of ""n"" electrons): A galvanic cell consists of two half-cells, such that the electrode of

neg: Electrolytic cell the cell, to be oxidized by depositing electrons on the electrode. To an external wire connected to the electrodes of a Galvanic cell (or battery), forming an electric circuit, the cathode is positive and the anode is negative. Thus positive electric current flows from the cathode to the anode through the external circuit in the case of a Galvanic cell. Consider two voltaic cells of unequal voltage. Mark the positive and negative electrodes of each one as P and N, respectively. Place them in a circuit with P near P and N near N, so the cells will tend to

neg: Galvanic cell "T" is the temperature in kelvins. For the Daniell cell "K" is approximately equal to . Thus, at equilibrium, a few electrons are transferred, enough to cause the electrodes to be charged. Actual half-cell potentials must be calculated by using the Nernst equation as the solutes are unlikely to be in their standard states, where "Q" is the reaction quotient. When the charges of the ions in the reaction are equal, this simplifies to where {M} is the activity of the metal ion in solution. In practice concentration in mol/L is used in place of activity. The metal electrode is

neg: Solid oxide fuel cell what most people refer to as an "SOFC stack". The ceramics used in SOFCs do not become electrically and ionically active until they reach very high temperature and as a consequence, the stacks have to run at temperatures ranging from 500 to 1,000 °C. Reduction of oxygen into oxygen ions occurs at the cathode. These ions can then diffuse through the solid oxide electrolyte to the anode where they can electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons. These electrons then flow through an external circuit where they can do

neg: Dye-sensitized solar cell can excite electrons that then flow into the titanium dioxide. The electrons flow toward the transparent electrode where they are collected for powering a load. After flowing through the external circuit, they are re-introduced into the cell on a metal electrode on the back, flowing into the electrolyte. The electrolyte then transports the electrons back to the dye molecules. Dye-sensitized solar cells separate the two functions provided by silicon in a traditional cell design. Normally the silicon acts as both the source of photoelectrons, as well as providing the electric field to separate the charges and create a current. In

neg: Galvanic cell one looks up copper and zinc's half reactions and finds: Thus the overall reaction is: The standard potential for the reaction is then +0.34 V − (−0.76 V) = 1.10 V. The polarity of the cell is determined as follows. Zinc metal is more strongly reducing than copper metal because the standard (reduction) potential for zinc is more negative than that of copper. Thus, zinc metal will lose electrons to copper ions and develop a positive electrical charge. The equilibrium constant, "K", for the cell is given by where "F" is the Faraday constant, "R" is the gas constant and

neg: Cathodic protection over a decade and incorporate the coordination, monitoring and high restorative current flow of ICCP systems with the reactive, lower cost and easier to maintain galvanic anodes. The system is made up of wired galvanic anodes in arrays typically 400mm apart which are then initially powered for a short period to restore the concrete and power ionic migration. The power supply is then taken away and the anodes simply attached to the steel as a galvanic system. More powered phases can be administered if needed. Like Galvanic systems corrosion rate monitoring from polarisation tests and half-cell potential mapping can be

neg: Corrosion Galvanic corrosion is often prevented by the use of sacrificial anodes. In any given environment (one standard medium is aerated, room-temperature seawater), one metal will be either more "noble" or more "active" than others, based on how strongly its ions are bound to the surface. Two metals in electrical contact share the same electrons, so that the "tug-of-war" at each surface is analogous to competition for free electrons between the two materials. Using the electrolyte as a host for the flow of ions in the same direction, the noble metal will take electrons from the active one. The resulting mass

neg: Dye-sensitized solar cell in the n-type portion flow into the p-type to "fill in" the missing electrons, also known as electron holes. Eventually enough electrons will flow across the boundary to equalize the Fermi levels of the two materials. The result is a region at the interface, the p-n junction, where charge carriers are depleted and/or accumulated on each side of the interface. In silicon, this transfer of electrons produces a potential barrier of about 0.6 to 0.7 V. When placed in the sun, photons of the sunlight can excite electrons on the p-type side of the semiconductor, a process known as photoexcitation.

neg: Dye-sensitized solar cell In silicon, sunlight can provide enough energy to push an electron out of the lower-energy valence band into the higher-energy conduction band. As the name implies, electrons in the conduction band are free to move about the silicon. When a load is placed across the cell as a whole, these electrons will flow out of the p-type side into the n-type side, lose energy while moving through the external circuit, and then flow back into the p-type material where they can once again re-combine with the valence-band hole they left behind. In this way, sunlight creates an electric current. In

neg: Primary cell voltage on the cathode must be higher than the voltage on the anode, creating an electric field directed from cathode to anode, to force the positive charge out of the cathode through the resistance of the external circuit. Inside the cell the anode is the electrode where chemical oxidation occurs, as it donates electrons which flow out of the anode into the external circuit. The cathode is the electrode where chemical reduction occurs, as it accepts electrons from the circuit through the cathode. Outside the cell, different terminology is used. As the anode donates positive charge to the electrolyte (thus

neg: Heterogeneous water oxidation substituted magnesium ferrite. Hydronium ions get trapped inside nanopores of ferrite that generate enough electrostatic fields to dissociate further water molecules into ions. Hydroxide ions instantly forms zinc hydroxide at the zinc electrode, releasing two electrons at the site of oxidation, the anode. The electrons are collected on another silver electrode at the site of reduction, the cathode, which converts hydronium ions into hydrogen gas and water. There is a net flow of current in the cell which can be used to do work. The reaction mechanism of the cell is expressed as: The overall HEC voltage is Ecell =

neg: Thermogalvanic cell equilibrium and, in doing so, produces a flow of chemical species and electrons. The electrons flow through the path of least resistance (the outer circuit) making it possible to extract power from the cell. Different thermogalvanic cells have been constructed attending to their uses and properties. Usually they are classified according to the electrolyte employed in each specific type of cell. In these cells the electrolyte between the electrodes is a water solution of some salt or hydrophylic compound. An essential property of these compounds is that they must be able to undergo redox reactions in order to shuttle electrons

neg: Oxygen sensor of closed-circuit rebreathers to keep the partial pressure of oxygen within safe limits. and to monitor the oxygen content of the breathing gas in saturation diving systems and of surface supplied mixed gas. This type of sensor operates by measuring the voltage generated by a small electro-galvanic fuel cell. In soil respiration studies oxygen sensors can be used in conjunction with carbon dioxide sensors to help improve the characterization of soil respiration. Typically, soil oxygen sensors use a galvanic cell to produce a current flow that is proportional to the oxygen concentration being measured. These sensors are buried at various

neg: Alkaline fuel cell producing water and releasing electrons. The electrons flow through an external circuit and return to the cathode, reducing oxygen in the reaction: formula_2 producing hydroxide ions. The net reaction consumes one oxygen molecule and two hydrogen molecules in the production of two water molecules. Electricity and heat are formed as by-products of this reaction. The two electrodes are separated by a porous matrix saturated with an aqueous alkaline solution, such as potassium hydroxide (KOH). Aqueous alkaline solutions do not reject carbon dioxide (CO) so the fuel cell can become "poisoned" through the conversion of KOH to potassium carbonate (KCO). Because

neg: Galvanic cell the ions of the more noble metal from plating out at the other electrode. A specific example is the Daniell cell (see figure), with a zinc (Zn) half-cell containing a solution of ZnSO (zinc sulfate) and a copper (Cu) half-cell containing a solution of CuSO (copper sulfate). A salt bridge is used here to complete the electric circuit. If an external electrical conductor connects the copper and zinc electrodes, zinc from the zinc electrode dissolves into the solution as Zn ions (oxidation), releasing electrons that enter the external conductor. To compensate for the increased zinc ion concentration, via the salt

neg: Anode Since the later discovery of the electron, an easier to remember and more durably correct technically although historically false, etymology has been suggested: anode, from the Greek "anodos", 'way up', 'the way (up) out of the cell (or other device) for electrons'. In electrochemistry, the "anode" is where oxidation occurs and is the positive polarity contact in an electrolytic cell. At the anode, anions (negative ions) are forced by the electrical potential to react chemically and give off electrons (oxidation) which then flow up and into the driving circuit. Mnemonics: LEO Red Cat (Loss of Electrons is Oxidation, Reduction occurs

neg: Electric current electric charge is in one direction only. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. An old name for direct current was "galvanic current". Natural observable examples of electrical current include lightning, static electric discharge, and the solar wind, the source of the polar auroras. Man-made occurrences of electric current include the flow of conduction electrons in metal wires

neg: Anode enter the device from the external circuit through the heated electrode. Therefore this electrode is permanently named the cathode, and the electrode through which the electrons exit the tube is named the anode. The polarity of voltage on an anode with respect to an associated cathode varies depending on the device type and on its operating mode. In the following examples, the anode is negative in a device that provides power, and positive in a device that consumes power: In a discharging battery or galvanic cell (diagram at right), the anode is the negative terminal because it is where conventional

neg: Electrochemical cell into electrical energy. A simple cell does this by using a combination of two metals (electrodes) and an electrolyte solution (which could be acid/alkali/salt solution). Metals can conduct electricity due to metallic bonding. Metallic bonds are the electrostatic force of attraction between negatively charged delocalised electrons and the positively charged metal ions. Metal atoms are surrounded by a “sea” of delocalised electrons. This means they are free to move within the structure- this gives metals its conducting abilities as an electric current can flow through it. A reaction between metals where electrons are gained is called a reduction reaction A

neg: Photoelectrochemical cell titanium dioxide). Photoelectrochemical cell Photoelectrochemical cells or PECs are solar cells that produce electrical energy or hydrogen in a process similar to the electrolysis of water. This type of cell electrolizes water to hydrogen and oxygen gas by irradiating the anode with electromagnetic radiation. This has been referred to as artificial photosynthesis and has been suggested as a way of storing solar energy in hydrogen for use as fuel. Incoming sunlight excites free electrons near the surface of the silicon electrode. These electrons flow through wires to the stainless steel electrode, where four of them react with four water molecules

neg: Photoelectrochemical cell Photoelectrochemical cell Photoelectrochemical cells or PECs are solar cells that produce electrical energy or hydrogen in a process similar to the electrolysis of water. This type of cell electrolizes water to hydrogen and oxygen gas by irradiating the anode with electromagnetic radiation. This has been referred to as artificial photosynthesis and has been suggested as a way of storing solar energy in hydrogen for use as fuel. Incoming sunlight excites free electrons near the surface of the silicon electrode. These electrons flow through wires to the stainless steel electrode, where four of them react with four water molecules to form

neg: Leclanché cell cell begins when zinc atoms on the surface of the anode oxidize, i.e. they give up both their valence electrons to become positively charged Zn ions. As the Zn ions move away from the anode, leaving their electrons on its surface, the anode becomes more negatively charged than the cathode. When the cell is connected in an external electrical circuit, the excess electrons on the zinc anode flow through the circuit to the carbon rod, the movement of electrons forming an electric current. After passing through the whole circuit, when the electrons enter the cathode (carbon rod), they combine with

neg: Galvanic cell each other in the presence of an electrolyte, such as salt water, forming a galvanic cell with H formation on the more noble metal. The resulting electrochemical potential then develops an electric current that electrolytically dissolves the less noble material. A concentration cell can be formed if the same metal is exposed to two different concentrations of electrolyte. Galvanic cell A galvanic cell or voltaic cell, named after Luigi Galvani or Alessandro Volta, respectively, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals immersed in

neg: Nanoelectronics electrochemical device, like a fuel cell or galvanic cell, but drawing power from blood glucose in a living body, much the same as how the body generates energy from food. To achieve the effect, an enzyme is used that is capable of stripping glucose of its electrons, freeing them for use in electrical devices. The average person's body could, theoretically, generate 100 watts of electricity (about 2000 food calories per day) using a bio-nano generator. However, this estimate is only true if all food was converted to electricity, and the human body needs some energy consistently, so possible power generated

neg: Zinc continued researching the effect and invented the Voltaic pile in 1800. The basic unit of Volta's pile was a simplified galvanic cell, made of plates of copper and zinc separated by an electrolyte and connected by a conductor externally. The units were stacked in series to make the Voltaic cell, which produced electricity by directing electrons from the zinc to the copper and allowing the zinc to corrode. The non-magnetic character of zinc and its lack of color in solution delayed discovery of its importance to biochemistry and nutrition. This changed in 1940 when carbonic anhydrase, an enzyme that scrubs

neg: Galvanic cell Galvanic cell A galvanic cell or voltaic cell, named after Luigi Galvani or Alessandro Volta, respectively, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals immersed in an electrolyte, or of individual half-cells with different metals and their ions in solution connected by a salt bridge or separated by a porous membrane. Volta was the inventor of the voltaic pile, the first electrical battery. In common usage, the word "battery" has come to include a single galvanic cell, but a battery properly consists of multiple

neg: Cathode electrons is almost always from anode to cathode outside of the cell or device, regardless of the cell or device type and operating mode. An exception is in a diode, where electrons flow from the cathode to the anode under a forward-bias. Cathode polarity with respect to the anode can be positive or negative depending on how the device is being operated. 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

neg: Electrochemical cell KNO NaCl, or some other electrolyte) is often employed to provide ionic contact between two half-cells with different electrolytes, yet prevent the solutions from mixing and causing unwanted side reactions. An alternative to a salt bridge is to allow direct contact (and mixing) between the two half-cells, for example in simple electrolysis of water. As electrons flow from one half-cell to the other through an external circuit, a difference in charge is established. If no ionic contact were provided, this charge difference would quickly prevent the further flow of electrons. A salt bridge allows the flow of negative or positive

neg: Alessandro Volta with brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies. In this way he discovered the electrochemical series, and the law that the electromotive force (emf) of a galvanic cell, consisting of a pair of metal electrodes separated by electrolyte, is the difference between their two electrode potentials (thus, two identical electrodes and a common electrolyte give zero net emf). This may be called Volta's Law of the electrochemical series. In 1800, as the result of a professional disagreement over the galvanic response advocated by Galvani, Volta invented the voltaic pile,

neg: Galvanic isolation Galvanic isolation Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow; no direct conduction path is permitted. Energy or information can still be exchanged between the sections by other means, such as capacitance, induction or electromagnetic waves, or by optical, acoustic or mechanical means. Galvanic isolation is used where two or more electric circuits must communicate, but their grounds may be at different potentials. It is an effective method of breaking ground loops by preventing unwanted current from flowing between two units sharing a ground conductor. Galvanic isolation is also used for safety,

neg: Electro-galvanic oxygen sensor on the oxygen reaching the anode from the sensor membrane. Lifetime is measured in oxygen-hours, and also depends on temperature and humidity The oxygen content of a stored gas mixture can be analysed by passing a small flow of the gas over a recently calibrated cell for long enough that the output stabilises. The stable output represents the fraction of oxygen in the mixture. Care must be taken to ensure that the gas flow is not diluted by ambient air, as this would affect the reading. The partial pressure of oxygen in anaesthetic gases is monitored by siting the cell

neg: Fuel Cell and Hydrogen Energy Association a completely harmless byproduct. Fuel cells produce an electrical current that can then be used outside the cell to do work. First, hydrogen atoms have their electrons removed through chemical reaction when they enter the cell at the anode, resulting in a positively charged hydrogen atom. Oxygen then enters the cell through the cathode where it combines with electrons returning from the electrical circuit and hydrogen ions that have traveled through the electrolyte (a piece of the fuel cell that carries electrically charged particles from one electrode to the other). The electrolyte is responsible for only allowing the correct ions

neg: Electrochemistry includes the Galvanic cell or Voltaic cell, named after Luigi Galvani and Alessandro Volta, both scientists who conducted several experiments on chemical reactions and electric current during the late 18th century. Electrochemical cells have two conductive electrodes (the anode and the cathode). The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place. Electrodes can be made from any sufficiently conductive materials, such as metals, semiconductors, graphite, and even conductive and electric polymers. In between these electrodes is the electrolyte, which contains ions that can freely move. The galvanic cell

neg: Shockley–Queisser limit thermal and certain other solar energy systems. In the extreme limit, for a tandem solar cell with an infinite number of layers, the corresponding limit is 86.8% using concentrated sunlight. (See Solar cell efficiency.) In a traditional solid-state semiconductor such as silicon, a solar cell is made from two doped crystals, one an n-type semiconductor, which has extra free electrons, and the other a p-type semiconductor, which is lacking free electrons, referred to as "holes." When initially placed in contact with each other, some of the electrons in the n-type portion will flow into the p-type to "fill in" the

neg: Galvanic isolation electric shock if the razor should be dropped into water. Galvanic isolation Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow; no direct conduction path is permitted. Energy or information can still be exchanged between the sections by other means, such as capacitance, induction or electromagnetic waves, or by optical, acoustic or mechanical means. Galvanic isolation is used where two or more electric circuits must communicate, but their grounds may be at different potentials. It is an effective method of breaking ground loops by preventing unwanted current from flowing between two units sharing

neg: Disulfide oxidoreductase D in the DsbD model proposed by Katzen and Beckwith (2000). This dithiol then donates electrons to the periplasmic C-terminal thioredoxin motif (CXXC) of DsbD, thereby reducing C461 and C464 (C6 and C7, respectively). This dithiol pair attacks the periplasmic N-terminal disulfide bridge at C103 and C109 (C1 and C2, respectively) which transfers electrons to DsbC and other protein electron acceptors as noted above. DsbD catalyses an essentially irreversible reaction due to the fact that electrons flow down their electrochemical gradient from inside the cell (negative inside) to outside the cell (positive outside). In order to reverse the reaction, electrons are

neg: Galvanic cell is to identify the two metals and their ions reacting in the cell. Then one looks up the standard electrode potential, "E", in volts, for each of the two half reactions. The standard potential of the cell is equal to the more positive "E" value minus the more negative "E" value. For example, in the figure above the solutions are CuSO and ZnSO. Each solution has a corresponding metal strip in it, and a salt bridge or porous disk connecting the two solutions and allowing ions to flow freely between the copper and zinc solutions. To calculate the standard potential

neg: Electrolytic cell water, particularly when ions are added (salt water or acidic water), can be "electrolyzed" (subject to electrolysis). When driven by an external source of voltage, H ions flow to the cathode to combine with electrons to produce hydrogen gas in a reduction reaction. Likewise, OH ions flow to the anode to release electrons and an H ion to produce oxygen gas in an oxidation reaction. In molten sodium chloride, when a current is passed through the salt the anode oxidizes chloride ions (Cl) to chlorine gas, releasing electrons to the anode. Likewise the cathode reduces sodium ions (Na), which accept

neg: Galvanic cell assumption that all chemical reactions are in equilibrium. When a current flows in the circuit, equilibrium conditions are not achieved and the cell voltage will usually be reduced by various mechanisms, such as the development of overpotentials. Also, since chemical reactions occur when the cell is producing power, the electrolyte concentrations change and the cell voltage is reduced. A consequence of the temperature dependency of standard potentials is that the voltage produced by a galvanic cell is also temperature dependent. Galvanic corrosion is a process that degrades metals electrochemically. This corrosion occurs when two dissimilar metals are in contact with

neg: Galvanic cell call the work function of the electrode. This view ignored the chemical reactions at the electrode-electrolyte interfaces, which include H formation on the more noble metal in Volta's pile. Although Volta did not understand the operation of the battery or the galvanic cell, these discoveries paved the way for electrical batteries; Volta's cell was named an IEEE Milestone in 1999. Some forty years later, Faraday (see Faraday's laws of electrolysis) showed that the galvanic cell -- now often called a voltaic cell -- was chemical in nature. Faraday introduced new terminology to the language of chemistry: electrode (cathode and anode),

neg: Fuel cell the fuel cell. At the anode a catalyst causes the fuel to undergo oxidation reactions that generate protons (positively charged hydrogen ions) and electrons. The protons flow from the anode to the cathode through the electrolyte after the reaction. At the same time, electrons are drawn from the anode to the cathode through an external circuit, producing direct current electricity. At the cathode, another catalyst causes hydrogen ions, electrons, and oxygen to react, forming water. Fuel cells are classified by the type of electrolyte they use and by the difference in startup time ranging from 1 second for proton exchange

neg: Thermogalvanic cell will flow through the circuit. A thermogalvanic cell can be seen as analogous to a concentration cell but instead of running on differences in the concentration/pressure of the reactants they make use of differences in the "concentrations" of thermal energy. The principal application of thermogalvanic cells is the production of electricity from low-temperature heat sources (waste heat and solar heat). Their energetic efficiency is low, in the range of 0.1% to 1% for conversion of heat into electricity. The use of heat to empower galvanic cells was first studied around 1880. However it was not until the decade of 1950

neg: Galvanic anode a chemical reaction occurring by an electrochemical mechanism (a redox reaction). During corrosion there are two reactions, oxidation (equation ), where electrons leave the metal (and results in the actual loss of metal) and reduction, where the electrons are used to convert water or oxygen to hydroxides (equations and ). In most environments, the hydroxide ions and ferrous ions combine to form ferrous hydroxide, which eventually becomes the familiar brown rust: As corrosion takes place, oxidation and reduction reactions occur and electrochemical cells are formed on the surface of the metal so that some areas will become anodic (oxidation) and

neg: Electro-galvanic oxygen sensor Electro-galvanic oxygen sensor An electro-galvanic fuel cell is an electrochemical device which consumes a fuel to produce an electrical output by a chemical reaction. One form of electro-galvanic fuel cell based on the oxidation of lead is commonly used to measure the concentration of oxygen gas in underwater diving and medical breathing gases. Electronically monitored or controlled diving rebreather systems, saturation diving systems, and many medical life-support systems use galvanic oxygen sensors in their control circuits to directly monitor oxygen partial pressure during operation. They are also used in oxygen analysers in recreational, technical diving and surface supplied mixed gas

neg: Electro-galvanic oxygen sensor Administration, NURC (NATO Undersea Research Centre), and Diving Diseases Research Centre. Electro-galvanic oxygen sensor An electro-galvanic fuel cell is an electrochemical device which consumes a fuel to produce an electrical output by a chemical reaction. One form of electro-galvanic fuel cell based on the oxidation of lead is commonly used to measure the concentration of oxygen gas in underwater diving and medical breathing gases. Electronically monitored or controlled diving rebreather systems, saturation diving systems, and many medical life-support systems use galvanic oxygen sensors in their control circuits to directly monitor oxygen partial pressure during operation. They are also used in

neg: Charge carrier carriers by leaving behind holes (electrons) in the other band. In other words, charge carriers are particles/electrons that are free to move (carry the charge). They get charged at the battery/cell, and then flow throughout the circuit, giving energy to any components in the way, then when out of charge and towards the end of the circuit, they get re-charged by the battery/cell. Charge carrier In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes.

neg: Overpotential cell's thermodynamic potential divided by the cell's experimental potential converted to a percentile. For a "galvanic" cell it is the ratio of a cell's experimental potential divided by the cell's thermodynamic potential converted to a percentile. Voltage efficiency should not be confused with Faraday efficiency. Both terms refer to a mode through which electrochemical systems can lose energy. Energy can be expressed as the product of potential, current and time (joule = volt × Ampere × second). Losses in the potential term through overpotentials are described by voltage efficiency. Losses in the current term through misdirected electrons are described by

neg: Electro-galvanic oxygen sensor diving to analyse the proportion of oxygen in a nitrox, heliox or trimix breathing gas before a dive. These cells are lead/oxygen galvanic cells where oxygen molecules are dissociated and reduced to hydroxyl ions at the cathode. The ions diffuse through the electrolyte and oxidize the lead anode. A current proportional to the rate of oxygen consumption is generated when the cathode and anode are electrically connected through a resistor The cell reaction for a lead/oxygen cell is: 2Pb+O=2PbO, made up of the cathode reaction: O2+2HO+4e-4OH, and anode reaction: 2Pb+4OH-2PbO+2HO + 4e. The cell current is proportional to the rate

neg: Phonovoltaic than generate an electron-hole pair, that is where formula_7 is the rate of generation and formula_8 is the rate of downconversion, i.e., the rate at which an optical phonon produces multiple low-energy, acoustic phonons. This provides a second entropy flow reducing the efficiency of a pV cell. Finally, entropy is generated in both pV and PV cells due to the inefficient separation of the generated electrons and holes. This efficiency (formula_9) is limited by the Carnot efficiency given by where formula_10 is the temperature of the pV cell and formula_11 is the temperature of the optical phonon population, as dictated

neg: Contact electrification Galvanic cell or battery. "See also: Dry pile" If two metals having differing work functions are touched together, one steals electrons from the other, and the opposite net charges grow larger and larger; this is the Volta effect. The process is halted when the difference in electric potential (electrostatic potential) between the two metals reaches a particular value, namely the difference in work function values - usually less than one volt. At this point, the Fermi levels for the two metals are equal, and there is no voltage difference between them. [If there were a voltage difference between them, then

neg: Depolarizer thus current to be reduced, especially if the bubbles cover a large fraction of a plate. Depolarizers are substances which are intended to remove the hydrogen, and therefore, they help to keep the voltage at a high level. However, this concept is outdated, since if enough depolarizer is present, it will react directly in most cases by getting electrons from the positive plate of the galvanic cell, i.e. there will be no relevant amount of hydrogen gas present. Therefore, the original concept of polarization does not apply to most batteries, and the depolarizer does not react with hydrogen as H.

neg: Galvanic cell d-orbital bonding, have higher cohesive energies (i.e. they are more weakly bonded) than all transition metals, including Cu, and are therefore useful as high-energy anode metals. The difference between the metals' ionization energies in water is the other energetic contribution that can drive the reaction in a galvanic cell; it is not important in the Daniell cell because the energies of hydrated Cu and Zn ions happen to be similar. Both atom transfer, e.g. of zinc from the metal electrode into the solution, and electron transfer, from metal atoms or to metal ions, play important roles in a galvanic cell.

neg: Electro-galvanic oxygen sensor pressure than 1 bar. This procedure may be done automatically, where the system has been designed to do it, or the diver can manually perform a "diluent flush" at any depth at which the diluent is breathable to compare the cell P readings against a known F and absolute pressure to verify the displayed values. This test does not only validate the cell. If the sensor does not display the expected value, it is possible that the oxygen sensor, the pressure sensor(depth), or the gas mixture F, or any combination of these may be faulty. As all three of these

neg: Electrochemical cell primary battery in high end products. A secondary cell, commonly referred to as a "rechargeable battery" is an electrochemical cell that can be run as both a galvanic cell or as an electrolytic cell. This is used as a convenient way to store electricity, when current flows one way the levels of one or more chemicals build up (charging), while it is discharging they reduce and the resulting electromotive force can do work. A "fuel cell" is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuel with oxygen or

neg: Shockley–Queisser limit As the name implies, electrons in the conduction band are free to move about the semiconductor. When a load is placed across the cell as a whole, these electrons will flow from the p-type side into the n-type side, lose energy while moving through the external circuit, and then go back into the p-type material where they can re-combine with the valence-band holes they left behind. In this way, sunlight creates an electric current. The Shockley–Queisser limit is calculated by examining the amount of electrical energy that is extracted per photon of incoming sunlight. There are several considerations: Any material,

neg: Erotic electrostimulation multiple channels (e.g. for several users or body regions) should have a small pulse isolation transformer for galvanic isolation in each channel, such that currents cannot flow across the body between channels. Pulse frequency, duration and amplitude should be selected to achieve the desired stimulation with the least amount of power delivered into the body, for example avoiding current during the refractory period after each action potential, where neurons do not respond to stimuli. Typical erotic electrostimulation devices use pulse frequencies in the range 300–3000 Hz, where skin nerves are most sensitive. A few cases of accidental death as a

neg: Cathodic protection load line in an area to avoid mechanical damage. The current density required for protection is a function of velocity and considered when selecting the current capacity and location of anode placement on the hull. Some ships may require specialist treatment, for example aluminium hulls with steel fixtures will create an electrochemical cell where the aluminium hull can act as a galvanic anode and corrosion is enhanced. In cases like this, aluminium or zinc galvanic anodes can be used to offset the potential difference between the aluminium hull and the steel fixture. If the steel fixtures are large, several galvanic

neg: Photoheterotroph they use a bacteriochlorophyll-based reaction center, or they use a bacteriorhodopsin. The chlorophyll-based mechanism is similar to that used in photosynthesis, where light excites the molecules in a reaction center and causes a flow of electrons through an electron transport chain (ETS). This flow of electrons through the proteins causes hydrogen ions to be pumped across a membrane. The energy stored in this proton gradient is used to drive ATP synthesis. Unlike in photoautotrophs, the electrons flow only in a cyclic pathway: electrons released from the reaction center flow through the ETS and return to the reaction center. They are

neg: Phenotype microarray in environmental conditions where cellular replication (growth) may not be possible, and that respiration reactions are usually detected much earlier than cellular growth. A sole carbon source that can be transported into a cell and metabolized to produce NADH engenders a redox potential and flow of electrons to reduce a tetrazolium dye, such as tetrazolium violet, thereby producing purple color. The more rapid this metabolic flow, the more quickly purple color forms. The formation of purple color is a positive reaction. interpreted such that the sole carbon source is used as an energy source. A microplate reader and incubation facility

neg: Electro-galvanic oxygen sensor of the failure of the sensors, which is generally not realistic. Factors which make the cell outputs in a rebreather statistically dependent include: This statistical dependency can be minimised and mitigated by: An alternative method of providing redundancy in the control system is to recalibrate the sensors periodically during the dive by exposing them to a flow of either diluent or oxygen or both at different times, and using the output to check whether the cell is reacting appropriately to the known gas as the known depth. This method has the added advantage of allowing calibration at higher oxygen partial

neg: ISO 31-8 or molecule have the following meanings and positions: pH is defined operationally as follows. For a solution X, first measure the electromotive force "E" of the galvanic cell and then also measure the electromotive force "E" of a galvanic cell that differs from the above one only by the replacement of the solution X of unknown pH, pH(X), by a solution S of a known standard pH, pH(S). Then obtain the pH of X as where Defined this way, pH is a quantity of dimension 1, that is it has no unit. Values pH(S) for a range of standard solutions

neg: Galvanic bath Galvanic bath Galvanic bath is an alternative medical treatment (a type of electrotherapy) based on the simultaneous use of water and electric current. The patient lies in a 34 degree Celsius bath, while gentle electric current is passed through his body. Galvanic baths are mostly used in the treatment of degenerative diseases such as inflammatory arthritis and problems with the joints. The treatment lasts about 15 minutes. In addition to full galvanic baths, when the patient's body is fully immersed in water, there are also "four-chambered galvanic baths" (also called "four cell galvanic baths"), which also combine electrical energy and

neg: Electric battery developments include batteries with embedded electronics such as USBCELL, which allows charging an AA battery through a USB connector, nanoball batteries that allow for a discharge rate about 100x greater than current batteries, and smart battery packs with state-of-charge monitors and battery protection circuits that prevent damage on over-discharge. Low self-discharge (LSD) allows secondary cells to be charged prior to shipping. Many types of electrochemical cells have been produced, with varying chemical processes and designs, including galvanic cells, electrolytic cells, fuel cells, flow cells and voltaic piles. A "wet cell" battery has a liquid electrolyte. Other names are "flooded cell",

neg: Galvanic series the anode (electron or anion attractor) within the electrolyte device functioning as described above (a galvanic cell). Galvanic reaction is the principle upon which batteries are based. See the "table" of standard electrode potentials for more details. The following is the galvanic series for stagnant (that is, low oxygen content) seawater. The order may change in different environments. Galvanic series The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience galvanic corrosion. The rate of

neg: Electrochemical cell was the inventor of the voltaic pile, the first electrical battery. In common usage, the word "battery" has come to include a single galvanic cell, but a battery properly consists of multiple cells. A primary cell is a Galvanic battery that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery). In general, the electrochemical reaction occurring in the cell is not reversible, rendering the cell unrechargeable. As a primary cell is used, chemical reactions in the battery use up the chemicals that generate the power; when they are

neg: Nano-RAM surrounding dielectric, any electrons placed on the FG will be trapped on the FG which screens the CG from the channel of the transistor and modifies the threshold voltage (VT) of the transistor. By writing and controlling the amount of charge placed on the FG, the FG controls the conduction state of the MOSFET flash device depending on the VT of the cell selected. The current flowing through the MOSFET channel is sensed to determine the state of the cell forming a binary code where a 1 state (current flow) when an appropriate CG voltage is applied and a 0

neg: Electron beam-induced current the electron–hole pairs will be separated by drift due to the electric field. If the p- and n-sides (or semiconductor and Schottky contact, in the case of a Schottky device) are connected through a picoammeter, a current will flow. EBIC is best understood by analogy: in a solar cell, photons of light fall on the entire cell, thus delivering energy and creating electron hole pairs, and cause a current to flow. In EBIC, energetic electrons take the role of the photons, causing the EBIC current to flow. However, because the electron beam of an SEM or STEM is very small,

neg: Electrochemical cell cell is discharged, the concentration of the reactants decreases and the cell potential also decreases. Electrochemical cell An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic cells or galvanic cells and the other ones are called electrolytic cells which are used to drive chemical reactions like electrolysis. A common example of a galvanic cell is a standard 1.5 volt cell meant for consumer use. A "battery" consists of one or more cells, connected either in

neg: Electric current is defined as moving in the same direction as the positive charge flow. So, in metals where the charge carriers (electrons) are negative, conventional current is in the opposite direction as the electrons. In conductors where the charge carriers are positive, conventional current is in the same direction as the charge carriers. In a vacuum, a beam of ions or electrons may be formed. In other conductive materials, the electric current is due to the flow of both positively and negatively charged particles at the same time. In still others, the current is entirely due to positive charge flow. For

neg: Geothrix fermentans endogenous electron-shuttling compounds. Electricity can be generated in "microbial fuel cells" which harness this flow of electrons from the bacterial cell to an anode. The advantage "G. fermentans" has by being able to reduce Fe(III) from a distance in a natural setting does not translate into an advantage in microbial fuel cells. Once the electrons have been transferred from the shuttling compound to the anode, the compound is free to diffuse back to the cell, but great distances may cause the compound to be lost to the environment. The possibility of compound loss coupled with the great amount of energy

neg: Gastrobot anode chamber, the bacteria remove electrons from the organic material and pass the electrons to a carbon electrode. The electrons then move through the ion exchange membrane to the cathode chamber, where they combine with protons and oxygen to form water. The electrons flowing from the anode into the cathode terminals generate electrical current and voltage. From this point, research is exploring using a hydrogen fuel cell to amplify the energy from the microbial fuel cell. The hydrogen fuel cell would use microbial fuel cell byproducts to create more energy without having to consume more material. Gastrobot requirements include: The

neg: Microbial fuel cell the two chambers is a salt bridge or ion-exchange membrane. This last feature allows the protons produced, as described in "," to pass from the anode chamber to the cathode chamber. The reduced mediator carries electrons from the cell to the electrode. Here the mediator is oxidized as it deposits the electrons. These then flow across the wire to the second electrode, which acts as an electron sink. From here they pass to an oxidizing material. Also the hydrogen ions/protons are moved from the anode to the cathode via a proton exchange membrane such as nafion. They will move across

neg: Electrochemical cell Electrochemical cell An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic cells or galvanic cells and the other ones are called electrolytic cells which are used to drive chemical reactions like electrolysis. A common example of a galvanic cell is a standard 1.5 volt cell meant for consumer use. A "battery" consists of one or more cells, connected either in parallel, series or series-and-parallel pattern.<r: A cell is a device which can convert chemical energy

neg: Galvanic cell anode composed of cadmium mercury amalgam, and a cathode composed of pure mercury. The electrolyte is a (saturated) solution of cadmium sulfate. The depolarizer is a paste of mercurous sulfate. When the electrolyte solution is saturated, the voltage of the cell is very reproducible; hence, in 1911, it was adopted as an international standard for voltage. A battery is a set of galvanic cells that are connected together to form a single source of voltage. For instance, a typical 12V lead–acid battery has six galvanic cells connected in series with the anodes composed of lead and cathodes composed of lead

neg: Electrode potential Potential of a cell assembled of two electrodes can be determined from the two individual electrode potentials using or, equivalently, This follows from the IUPAC definition of the electric potential difference of a galvanic cell, according to which the electric potential difference of a cell is the difference of the potentials of the electrodes on the right and the left of the galvanic cell. When Δ"V" is positive, then positive electrical charge flows through the cell from the left electrode (anode) to the right electrode (cathode). Electrode potential Electrode potential, "E", in chemistry or electrochemistry, according to a IUPAC definition,

neg: Plasma display plasma display typically comprises millions of tiny compartments in between two panels of glass. These compartments, or "bulbs" or "cells", hold a mixture of noble gases and a minuscule amount of another gas (e.g., mercury vapor). Just as in the fluorescent lamps over an office desk, when a high voltage is applied across the cell, the gas in the cells forms a plasma. With flow of electricity (electrons), some of the electrons strike mercury particles as the electrons move through the plasma, momentarily increasing the energy level of the atom until the excess energy is shed. Mercury sheds the energy

neg: Power plant engineering sun. The new flow of electrons generates electricity within the cell. While PV's are an efficient method of producing electricity, they do burn out after a decade and thus, must be replaced; however, their efficiency, cost of operation, and lack of noise/physical pollutants make them one of the cleanest and least expensive forms of energy. Solar power plants require the work of many facets of engineering; electrical engineers are especially crucial in constructing the solar panels and connecting them into a grid, computer engineers code the cells themselves so that electricity can be effectively and efficiently produced, and civil engineers

neg: Sources of electrical energy field causes separation of these pairs, establishing an electromotive force in the process. The electric field sends the electron to the p-type material, and the hole to the n-type material. If an external current path is provided, electrical energy will be available to do work. The electron flow provides the current, and the cell's electric field creates the voltage. With both current and voltage the silicon cell has power. The greater the amount of light falling on the cell's surface, the greater is the probability of photons releasing electrons, and hence more electric energy is produced. When a zinc electrode

neg: Thermogalvanic cell Thermogalvanic cell A thermogalvanic cell is a kind of galvanic cell in which heat is employed to provide electrical power directly. These cells are electrochemical cells in which the two electrodes are deliberately maintained at different temperatures. This temperature difference generates a potential difference between the electrodes. The electrodes can be of identical composition and the electrolyte solution homogeneous. This is usually the case in these cells. This is in contrast to galvanic cells in which electrodes and/or solutions of different composition provide the electromotive potential. As long as there is a difference in temperature between the electrodes a current

neg: Galvanic cell Concentration cells, whose electrodes and ions are made of the same metal and which are driven by an entropy increase and free-energy decrease as ion concentrations equalize, show that the electronegativity difference of the metals is not the driving force of electrochemical processes. Galvanic cells and batteries are typically used as a source of electrical power. The energy derives from a high-cohesive-energy metal dissolving while to a lower-energy metal is deposited, and/or from high-energy metal ions plating out while lower-energy ions go into solution. Quantitatively, the electrical energy produced by a galvanic cell is approximately equal to the standard free-energy

neg: Galvanic cell of the two electrodes into the electrolyte. The emf depends on both the electrodes and on the electrolyte, an indication that the emf is chemical in nature. The electrochemical processes in a galvanic cell occur because reactants of high free energy (e.g. metallic Zn and hydrated Cu in the Daniell cell) are converted to lower-energy products (metallic Cu and hydrated Zn in this example). The difference in the lattice cohesive energies of the electrode metals is sometimes the dominant energetic driver of the reaction, specifically in the Daniell cell. Metallic Zn, Cd, Li, and Na, which are not stabilized by

neg: NDUFA13 Complex I and transfers two electrons to the isoalloxazine ring of the flavin mononucleotide (FMN) prosthetic arm to form FMNH. The electrons are transferred through a series of iron-sulfur (Fe-S) clusters in the prosthetic arm and finally to coenzyme Q10 (CoQ), which is reduced to ubiquinol (CoQH). The flow of electrons changes the redox state of the protein, resulting in a conformational change and p"K" shift of the ionizable side chain, which pumps four hydrogen ions out of the mitochondrial matrix. NDUFA13 has a homologous protein known as GRIM-19, a cell-death regulatory protein. It is involved in interferon/all-trans-retinoic acid (IFN/RA)

neg: Anode devices usually allow substantial current flow in one direction but negligible current in the other direction. Therefore the electrodes are named based on the direction of this "forward" current. In a diode the anode is the terminal through which current enters and the cathode is the terminal through which current leaves, when the diode is forward biased. The names of the electrodes do not change in cases where reverse current flows through the device. Similarly, in a vacuum tube only one electrode can emit electrons into the evacuated tube due to being heated by a filament, so electrons can only

neg: Concentration cell the active metal beneath the film will be exposed to corrosive attack in areas where the passive film is broken. An electrical potential will develop between the large area of the passive film (cathode) and the small area of the exposed active metal (anode). Rapid pitting of the active metal will result. Concentration cell In battery technology, a concentration cell is a limited form of a galvanic cell that has two equivalent half-cells of the same composition differing only in concentrations. One can calculate the potential developed by such a cell using the Nernst equation. A concentration cell produces a