Cathode Definition and 125 Threads

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 charges move. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit.
The electrode through which conventional current flows the other way, into the device, is termed an anode.

View More On Wikipedia.org
Recent contents Top users
  1. hagopbul

    Question about battery -- Looking into the electrode effects on the battery

    Hello All : i had few suggestions about battery enhancement using some ideas which i had just abstract understanding not enough even to suggest discussion but i have this question why we dont fold the anode and the cathode into geometrical shape , wouldnt that increase the number of...
  2. sol47739

    I Postive rays in cathode ray tube experiments?

    I read in the following book A history of the sciences by Stephen F. Mason. About the discovery of the electron the write what I attached in the picture. I wonder what do these positive rays traveling in the opposite direction they talk about consist of? Some ions or what? I understand that the...
  3. I

    Why is perforated cathode used in the discovery of anode rays?

    I really tried to solve it a lot and the info that I gathered is : Electrons or protons can be ABSORBED by cathode or anode so there must be some hole in the electrode for the rays to pass. These electrons ionize the gas and those positive gas ions move towards cathode.
  4. P

    I Exploring Cathode Rays & Anodes: A Visual Guide

    The attached diagram shows the cathode rays moving in straight lines forward but the anode is beneath them?
  5. Rongeet Banerjee

    What is the definition of cathode in the photoelectric effect?

    We know anode=oxidation=loss of electrons and cathode=reduction=gain of electrons but in the photoelectric effect the electrons are gained at the anode and lost at the cathode of the discharge tube? References: Anode, Cathode, Oxidation, Reduction
  6. O

    B Emission from a coated cathode and tunneling

    I am wondering about an exercise exam question (it isn't homework): "at low temperatures (<2000 K), thermionic emission of a tungsten cathode depends on tunneling. By coating the tungsten with a suitable substance, the emission by tunneling can be greatly increased. Question: which two...
  7. WMDhamnekar

    MHB Cathode & Anode: Explaining the Difference

    Hello, In cathode ray discharge tube,negative electrode is cathode and positive electrode is anode. But in case of direct current circuit, it is the positively charged terminal of a voltaic cell or storage battery that supplies current and anode is the negatively charged terminal of a voltaic...
  8. J

    Can solar heating of hot cathodes generate useful power?

    I know typically the hot cathode of an electron gun or vacuum tube is heated either directly or indirectly by electric resistance heating. What if the tungsten (cathode) were heated by another means, say focused sunlight? Electrons would still boil off through thermionic emission. If a small...
  9. garthenar

    Solving for a neutralizing B0 in a Thomson Cathode Ray (Algebra?)

    I've attached a picture from the problem, the given equations, and my work so far. I knew I had a problem when My units wouldn't check out. This should just be simple algebra but It's not working. Please help me to understand what I am doing wrong.
  10. A

    Obtain Cathode Ray Tubes Without X-rays

    Good Day, I would like to obtain cathode-ray tubes for deflecting electrons with a magnet. However, I don't want to deal with X-rays, and would prefer to obtain cathode tubes that cannot produce X-rays at all. I haven't had much luck on the internet finding such cathode ray tubes or I don't...
  11. Robin04

    Electrons in a cathode ray tube

    Homework Statement The accelerating voltage in a cathode ray tube is ##1000 V##, the electron current density is ##150 \mu A##. a) How many electrons arrive at the screen in a second? b) What's the magnitude of the force exerted on the screen by the electrons if they stop on collision? (Sorry...
  12. Dan Jenson

    E Field at a Glow Discharge Tube Cathode

    I am trying to understand the "strong" negative E field in the Aston Dark Space in the thin region close to the cathode or else even the cathode surface. See the diagram at: http://www.glow-discharge.com/?Physical_background:Glow_Discharges My question regards the "Electrical Field E" graph...
  13. A

    Why is the Anode of an LED Connected to Positive?

    So, I'm new to electronics and I started to build some circuits with LEDs. I read up on how LEDs work and how they consist of a doped semiconductor material etc. But when I actually went to wire the LED in, it said the anode should be connected to the positive terminal of the power source. I'm...
  14. A

    How Batteries Work: An Electrochemical Explanation

    So, I'm a little confused on how batteries work. I understand they convert chemical energy into electrical energy. I also understand that the battery consists of an anode and a cathode with an electolyte in the middle to force the electrons from the chemical reaction to have to follow the wires...
  15. srinaath

    Why do we need to supply air to the cathode of a hydrogen fuel cell

    I am trying to understand the working of simple hydrogen fuel cell. We have anode (negative terminal), cathode (positive terminal), catalyst at anode to separate negative and positive ions of hydrogen atoms and electrolyte which allows only positive ions. We will be sending hydrogen fuel at...
  16. H

    Electric field generation between anode and cathode

    Hi I'm running an experiment where I want to see the electrical field generated when I energise a submerged anode (an array consisting of 4 x stainless steel tubes spaced equidistance apart) and cathode array (similar to the anode) upstream and downstream of the flowing water tank (glass sided...
  17. dholbach

    Can a cathode ray tube be made from a light bulb?

    Light bulbs and cathode ray tubes are structurally similar in some respects. For example, both contain a filament -- in the light bulb, the filament heats up to produce light, while in a cathode ray tube, the filament emits electrons, which are then steered into a target (in a CRT TV, the...
  18. O

    Cathode ray tube, Voltage needed to move the beam impact spot

    Homework Statement Question: A cathode ray tube in a TV has an electron gun operating at 10 kV. a: What is the velocity (in m.s-1) at which the electrons are emitted? Answer:5.9x107 b: How many volts are needed between the deflector plates to move the beam impact spot across a 70 cm screen if...
  19. A

    Can one cathode transfer electrons to multiple anodes

    what if i have a cathode at one end of a tube and multiple anodes through out the tube with argon gas, will electrons flow from the one cathode to multiple anodes like curves -ve1 to +ve1 and -ve1 to +ve2 and -ve1 to +ve3 or there has to be only one cathode and one anode for electrons to flow (...
  20. C

    Momentum in a photon -> cathode collision

    Homework Statement A photon with the length of lambda hits a cathode perpendicularly to its surface. As a result, an electron leaves its surface perpendicularly to the direction of the photon. How much momentum was transferred from the photon to the cathode? The work function of the cathode is...
  21. D

    How Do You Calculate the Displacement in Thompson's Cathode Ray Tube Experiment?

    Homework Statement What is the distance Δy between the two points that you observe? Assume that the plates have length d, and use e and m for the charge and the mass of the electrons, respectively. Express your answer in terms of e, m, d, v0, L, and E0. Homework Equations kinematics...
  22. A

    Cathode Coatings for Electron Emission: Investigating Materials and Techniques

    Homework Statement What 3 materials is the cathode coated with, from which the electron originate? Homework Equations None The Attempt at a Solution From what I managed to find, I think some may be nickel and barium but I'm not sure.
  23. Planobilly

    Why is there a cathode to ground resistor on a KT66 power tube in an amp kit?

    There is a cathode to ground resistor on a KT66 power tube on a amp kit. The value is 1 ohm. I ASSUME the only reason for it being there would be to be able to measure the current flow. I ASSUME 1 ohm is not going to change the cathode bias. Is my assumption correct? The KT66 is a beam power...
  24. Chris Frisella

    EM Phenomenon: Magnetism from a Cathode Ray?

    I have recently studied about relativity being the reason for magnetism. The example given was about a magnetic field generated from current down a long wire. When two such wires with current in the same direction were parallel to each other there was an attractive force between them because...
  25. M

    Work function of cathode, visible light

    Homework Statement You need to design a photodetector that can respond to the entire range of visible light (400 nm - 700 nm). What is the maximum possible work function? Homework Equations E = hf = hc/lambda The Attempt at a Solution For 400nm, I got E = 3.11 eV and for 700nm I got 1.78 eV...
  26. J

    Water electrolysis with carbon cathode.

    I was wondering if I breakdown water with a carbon electrodes, will some methane be formed as well as hydrogen? In addition if methane is formed could other hydrocarbon chains also occur?
  27. S

    Trace of cathode ray in changing magnetic field.

    I know that cathode rays follow a helical pattern if they enter a uniform magnetic field at an angle less than 90 degrees. This leaves me with two questions. 1. If the cathode ray described above, hit a phosphor coated screen, would it show only 1 spot or a circle? 2. If the magnetic field was...
  28. prashant singh

    What Happens When You Connect a 10,000 V Supply to a Normal Tube Light?

    suppose I connect a 10,000 v supply to a normal tube light. what will happen? will it behave like a cathode ray tube or something else
  29. S

    Exploring the Wave-Particle Duality of Electrons in CRT Monitors

    How do CRTs work well and electrons can be sent to exact location on screen in CRT monitors if electrons can behave like wave? Is there something in old TVs (for example measurement device) along the road that electron travels to avoid behave like wave?
  30. A

    Calculate the electron kinetic energy ejected from cathode?

    I would like to calculate the electron kinetic energy ejected from a cathode as a function of the electric field and pressure without known of the temperature and velocity.
  31. Plat

    Striations in cathode ray discharge

    What causes these striations? How does the voltage and pressure of the discharge affect the size, color, number, and spacing of the striations? I have produced a discharge with striations with fairly low voltage (under 15kv) and pressure 10 - 100pa, and the striations are very thin, compact, and...
  32. Andrew Wang

    Cathode Ray Tube and magnetic field Question

    Homework Statement A cathode ray tube (CRT), consisting of an electron gun and a screen, is placed within a uniform constant magnetic field of magnitude B such that the magnetic field is parallel to the beam axis of the gun, as shown in figure...
  33. terryds

    Why cations migrate toward cathode?

    Why Na+ (which is positive in charge) migrate to the cathode which is also positive in charge?? They should repel each other right?
  34. Nemika

    Cathode ray tube- thermionic emission

    I have just learned about the cathode ray tube in the class room. There is a part called electron gun in it which emits electrons and these electrons finally strike the fluorescent screen.(I hope its correct till here.) But I want to ask that won't there be a loss of electrons in this process...
  35. B

    Cathode Ray Tube with magnetic field

    Homework Statement A solenoid is placed beneath a CRT that produces a magnetic field of 1.10 x -2. The CRT is 1 meter away from a screen. The electrons that make up the beam were accelerated from rest through a potential difference(V) at the beginning of the CRT. Acceleration of the electrons...
  36. N

    What Variables Can Be Changed in a Cathode Ray Tube Experiment?

    For my year 12 physics EEI (extended experimental investigation) i need to develop some sort of experiment with variables i can change to retrieve data from. I have a basic cathode ray tube from a few months ago much like the one in this video: . Does anyone have any idea of what variables i...
  37. AnkurGarg

    Electrochemical cell electrode potential difference

    In our textbook it is written that -voltmeter measures the electrode potential difference between 2 half cells (in an electrochemical cell) (electrode potential refers to the potential difference between electrode and its salt solution in which it is dipped) it should come-voltmeter measures...
  38. Quotes

    Where Is Carbon Used in Dry Cells?

    I was studying about dry cell and read that carbon(graphite) rod surrounded by MnO2 is used as cathode but when i read the chemical reaction equation at cathode given as : MnO2 + NH4+ + e - - - - > MnO(OH) +NH3 I nowhere found carbon... So where is it actually used? (i found this for mercury...
  39. 3

    A heated cathode inducing thermionic emission of electrons.

    Hello all. I have been looking at this problem: I wrote three equations there, one for each part, which I think will help me solve each part; is my approach to the problem using those equations that you see there correct? I am just looking for some advice on where and how to start this problem...
  40. J

    How many volts does a cathode ray tube emits?

    I don't know a lot about classical physics but I was wondering how many volts a cathode ray tube emits?
  41. S

    Accelerating electrons in a cathode ray tube

    I have a question which has intrigued me for quite some time. If the electrons are accelerated using a potential difference in a cathode ray tube, the electrons should get accelerated till the time they reach the anode only. Once they cross over (ie. move to the other side of the anode), they...
  42. gracy

    How cathode is positively charged in voltaic cell?

    How cathode is positively charged in voltaic cell?I mean at cathode reduction takes place ,but the electron which is gained for reduction comes from anode,than why cathode becomes positively charged ?As electrons are from anode not from cathode that means electrons are not lost by cathode ,so it...
  43. S

    Magnetic anode for copper cathode battery

    Hello everyone from the Physics Forums, I'm doing a school project and I'm looking for a potential anode alloy that is ferromagnetic which I could use with a copper cathode. I'm making a battery and I have to use copper as my cathode mainly because I have made the cathode cells structured...
  44. S

    Searching for best ferromagetic cathode for aluminum anode battery

    This is a list of ferromagnetic materials that I've found on Wikipedia's category ferromagnetic materials page. I was wondering which of these materials would make possibly great cathodes for aluminum anode in the application of creating an sulfuric solution based acid battery. The battery I...
  45. G

    J.J. Thomson's Cathode Ray Experiment: Discovery of Electrons

    Hi! I've been watching this video http://ocw.mit.edu/courses/chemistry/5-111-principles-of-chemical-science-fall-2008/video-lectures/lecture-2/ on the discovery of electrons , and I have some doubts about it. The lecturer explains the cathode ray experiment performed by J.J Thomson. This is...
  46. P

    Gate source voltage and gate cathode voltage

    I am studying thyrisors right now. I am really struck at trigger circuit . The book shows gate source voltage and gate chathode voltage as two different things. I fail to understand the difference and significance of them. Please help me out .
  47. A

    Will All Metals Deposit on the Copper Cathode in My Electrolysis Experiment?

    Hi. I am a complete novice working on my first backyard experiment. I have a 1part sulphuric acid 4parts tap water pregnant leach solution (from old copper mine tailings). If I were to set up an electrolysis type experiment with a lead anode and a copper cathode should I expect all the...
  48. Warpspeed13

    Will the material in a cathode be carried to the anode?

    If I were to strike an arc between a copper cathode and a tungsten anode would copper be deposited on the anode? If so how could I calculate deposition rate? I know this works in electroplating but will it work through air or another gas?
  49. S

    The need for electrolytes between cathode and anode in battery

    My question is simple: Why do batteries need electrolytes? Wouldn't the battery need the charge to flow only through the circuit in the device being powered? The point of the anode and cathode's separation is to preserve the potential difference, so why allow charge to flow through an electrolyte?
  50. M

    How Can I Design Experiments to Observe Different Fluorescence Effects in a CRT?

    Homework Statement I am building a CRT for my physics project but have some doubts. I know there will fluorescence effect but my project requires to do an experiment and make observations. So how can I relate this experiment so that I have:- 1. Different cases and experiments with the CRT...
Back
Top