cathode

Examples of cathode in the following topics:

• Cathode Ray Tube, TV and Computer Monitors, and the Oscilloscope

  • A cathode ray tube consists of a vacuum tube that contains one or more electron guns used to excite phosphors on a screen to produce images.
  • The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns (a source of directed electrons) and a fluorescent screen used to view images.
  • Identify the primary components of a cathode ray tube and describe the use of cathode ray tubes

• The Battery

  • One half-cell includes electrolyte and the anode, or negative electrode; the other half-cell includes electrolyte and the cathode, or positive electrode.
  • In the redox (reduction-oxidation) reaction that powers the battery, cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are removed) at the anode.
  • When a battery is connected to a circuit, the electrons from the anode travel through the circuit toward the cathode in a direct circuit.
  • Notice the positive cathode and negative anode.

• The Discovery of the Parts of the Atom

  • In 1869, he discovered a glow emitted from the cathode that increased in size with decrease in gas pressure.
  • Thomson performed experiments demonstrating that cathode rays were unique particles, rather than waves, atoms or molecules, as was believed earlier.
  • Thomson made good estimates of both the charge $e$ and the mass $m$, finding that cathode ray particles (which he called "corpuscles") had perhaps one thousandth the mass of hydrogen, the least massive ion known.
  • He showed that their charge to mass ratio (e/m) was independent of cathode material.

• The Physics of Bremsstrahlung

  • X-rays were first produced in the laboratory by accelerating electrons along a strong electric field (a typical potential difference of 10kV) from an anode to a cathode in vacuum.
  • When the electrons hit the thick metal cathode and stop (brake), they emit cathode rays or X-rays.

• Examples and Applications

  • All cavity magnetrons consist of a hot cathode with a high (continuous or pulsed) negative potential created by a high-voltage, direct-current power supply.
  • The cathode is built into the center of an evacuated, lobed, circular chamber.

• LCDs

  • Unlike the newer cathode ray tube (CRT) and plasma displays, LCDS do not use phosphors.

• Electron Microscopes

  • In the electron microscope, electrons which are emitted by a cathode are formed into a beam using magnetic lenses (usually electromagnets).

• X-Rays

  • X-rays can be generated by an x-ray tube, a vacuum tube that uses high voltage to accelerate the electrons released by a hot cathode to a high velocity.