Question regarding cathodes and anodes

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Discussion Overview

The discussion revolves around the concepts of cathodes and anodes, particularly in the contexts of chemistry and electronic devices like cathode-ray tubes. Participants explore the definitions and roles of these components, addressing potential confusion arising from their usage in different applications.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that in chemistry, the anode is the site of oxidation and the cathode is the site of reduction, while questioning if this applies similarly in electronic contexts.
  • One participant emphasizes that the cathode is always the terminal through which electrons flow into, suggesting a consistent definition across contexts.
  • Another participant challenges this by noting that in vacuum tubes, the cathode emits electrons, which flow towards the positively charged anode, leading to confusion regarding the definitions.
  • A participant proposes that the cathode is the source of electrons and the anode is the sink, indicating a difference in potential between the two.
  • There is mention of the ambiguity surrounding the terms, especially in rechargeable cells and diodes, raising questions about their roles depending on current flow direction.
  • One participant points out that electrons can enter and leave both the cathode and anode in a circuit, complicating the understanding of their functions based on context.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and roles of cathodes and anodes, with no consensus reached on a unified understanding. The discussion remains unresolved regarding the application of these terms across different contexts.

Contextual Notes

Participants highlight the context-sensitive nature of the definitions, noting that the roles of cathodes and anodes can vary significantly between chemical reactions and electronic devices, leading to potential misunderstandings.

collegelife101
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Hello everyone!

I just had a quick question regarding cathodes and anodes. In chemistry, I know that an anode is a site of oxidation and the cathode is the site of reduction. However, I noticed that with a cathode-ray tube, for instance, a cathode emits electrons to an anode?

Are these two the same things or not? Can someone please differentiate?

Thanks!
 
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collegelife101 said:
Hello everyone!

I just had a quick question regarding cathodes and anodes. In chemistry, I know that an anode is a site of oxidation and the cathode is the site of reduction. However, I noticed that with a cathode-ray tube, for instance, a cathode emits electrons to an anode?

Are these two the same things or not? Can someone please differentiate?

Thanks!
The important thing to remember is that cathode is negative and anode is positive.
That's the common thing in both Cathode-ray-tubes and electrolysis things IMO.
 
Cathode is always the one through which electrons flow into. Everything else should follow.
 
Borek said:
Cathode is always the one through which electrons flow into. Everything else should follow.

so why in a vacuum tube is the cathode emitting electrons and the positively charged anode "collecting" them "

I have always found it annoying/confusing when they say what you did for chemistry
but the opposite for tubes and semiconductor diodes

what is the reason for the difference ?

Dave
 
Borek said:
Cathode is always the one through which electrons flow into. Everything else should follow.

I don't think this is correct. As davenn has pointed out, in electron tubes/guns, the cathode is where the electrons originate and "flow out", not into. The anode is where they flow into.

The typical answer is that the cathode is the terminal with the lowest potential or the electron source while the anode is the highest potential or the electron sink.

Zz.
 
To be more pedantic:

Cathode is always the one that electrons flow into from outside the device.

Clearly the negative electric charge flowing into the cathode has to get to the anode somehow inside the device, either by negative charges moving one way, and/or by positive charges moving the other way.
 
Cathode is always the one that electrons flow into from outside the device.

yup, that's a clearer definition :) did see something along those lines in wiki

cheers
Dave
 
There can be a lot of confusion around this. I used to think I understood it, but no longer. The terms are best avoided in general conversation if you eschew ambiguity, IMO.

Do the terminals of a rechargeable cell take turns in being the anode? Do you connect the red charger lead to the cell's anode or its cathode?

Does the anode of a zener diode change depending on the direction of current flow??

Questions, questions ...
 
The problem is that the electrons flow in a circular path round a circuit and Kirchoff1 applies. So electrons actually enter and leave both the Cathode and the Anode. the effect of this is to confuse people as the rule is context sensitive. In a battery, electrons enter the cathode plate from the electrolyte but in a TV tube, they leave the Cathode into the vacuum. This is a great example of where trying blindly to learn a rule, without understanding, is deadly.
 

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