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Schematic symbol used in circuit diagrams for vacuum tube, showing cathode. A hot cathode is a cathode that is heated by a filament to produce electrons by thermionic emission. [4] [8] The filament is a thin wire of a refractory metal like tungsten heated red-hot by an electric current passing through it.
Cutaway diagram of a triode vacuum tube, showing the plate (anode) In electronic vacuum devices such as a cathode-ray tube, the anode is the positively charged electron collector. In a tube, the anode is a charged positive plate that collects the electrons emitted by the cathode through electric attraction.
The cathode is either indirectly heated or directly heated. If indirect heating is employed, a heater is included in the envelope. In operation, the cathode is heated to red heat, around 800–1,000 °C (1,470–1,830 °F). A directly heated cathode is made of tungsten wire and is heated by a current passed through it from an external voltage ...
Diagram of a battery with a polymer separator. A separator is a permeable membrane placed between a battery's anode and cathode.The main function of a separator is to keep the two electrodes apart to prevent electrical short circuits while also allowing the transport of ionic charge carriers that are needed to close the circuit during the passage of current in an electrochemical cell.
PEMFCs have a thin, polymeric membrane as the electrolyte. This membrane is located in between the anode and cathode catalysts and allows the passage of protons to pass to the cathode while restricting the passage of electrons. Compared to liquid electrolytes, a polymeric membrane has a much lower chance of leakage [2].
Schematic symbol used in circuit diagrams for a vacuum tube, showing control grid. The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode.
The cathode may be surrounded by a shield to prevent sputtering. [226] [227] The cathode is a layer of barium oxide which is coated on a piece of nickel for electrical and mechanical support. [228] [143] The barium oxide must be activated by heating to enable it to release electrons. Activation is necessary because barium oxide is not stable in ...
The cathode is coated with a mixture of alkaline earth oxides such as calcium and thorium oxide which reduces its work function so it produces more electrons. The grid is constructed of a helix or screen of thin wires surrounding the cathode. The anode is a cylinder or rectangular box of sheet metal surrounding the grid.