Cathode FAQs:


Q: Is a cathode the electrode from which a conventional current leaves a polarized electrical device?

A: Yes.

Q: Is a cathode the N–doped layer of the PN junction with a high density of free electrons due to doping?

A: Yes, and an equal density of fixed positive charges, which are the dopants that have been thermally ionized.

Q: Is a cathode where the positive pole is connected to allow the circuit to be completed: as the anode of the galvanic cell gives off electrons?

A: Yes, and they return from the circuit into the cell through the cathode.

Q: Is a cathode heated by the electron current flowing through it to a temperature at which thermionic emission occurs?

A: Yes.

Q: Is a cathode the electrode of an electrochemical cell at which reduction occurs?

A: Yes, a useful mnemonic to remember this is AnOx RedCat. Another mnemonic is to note the cathode has a 'c', as does 'reduction'. Hence, reduction at the cathode.

Q: Is a cathode a metal surface which emits free electrons into the evacuated space?

A: Yes.

Q: Is a cathode a cathode that is heated by a filament to produce electrons by thermionic emission?

A: Yes.

Q: Is a cathode continually replenished as it is lost by diffusion of thorium from the interior of the metal?

A: Yes.

Q: Were cathodes used in the first vacuum tubes?

A: Yes, but today they are only used in fluorescent tubes, some large transmitting vacuum tubes, and all X-ray tubes.

Q: Is a cathode the positive terminal since that is where the current flows out of the device?

A: Yes, This outward current is carried internally by positive ions moving from the electrolyte to the positive cathode. It is continued externally by electrons moving inwards, this negative charge moving inwards constituting positive current flowing outwards.

Q: Is a cathode to isolate the rest of the vacuum tube from the electric potential across the filament?

A: Yes.

Q: Is a cathode usually called the heater?

A: Yes.

Q: Is a cathode where the negative polarity is applied to drive the cell?

A: Yes.

Q: Is a cathode hydrogen gas or pure metal from metal ions?

A: Yes.

Q: Is a cathode covered with a coating of alkali metal oxides?

A: Yes, and often barium and strontium oxide.

Q: Is a cathode an electrode that emits electrons into the device?

A: Yes.

Q: Is a cathode the negative terminal at the pointed end of the arrow symbol?

A: Yes, where current flows out of the device.

Q: Are cathodes treated with chemicals?

A: Yes, and usually compounds of metals with a low work function.

Q: Is a cathode the negative terminal?

A: Yes, and from which current exits the device and returns to the external generator.

Q: Are cathodes used in most devices today?

A: Yes.

Q: Are cathodes used in vacuum tubes in radio transmitters and microwave ovens?

A: Yes, and to produce the electron beams in older cathode ray tube type televisions and computer monitors, in x-ray generators, electron microscopes, and fluorescent tubes.

Q: Is a cathode a nickel tube with the filament inside it?

A: Yes, and the heat from the filament causes the outside surface of the tube to emit electrons.