Cathode ray contradicts Chemistry? (1 Viewer)

[jamesfirst]

In Ideas and Implementation, the evacuation tube (forgot what it was called) has two electrodes and the cathode is the negative one???


In chemistry, production of materials, the anode is the negative electrode...??



My teacher says it's only in galvanic cell that the anode becomes negative.... what's going on. . lol

 

[ohexploitable]

An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID (Anode Current Into Device). (The direction of electric current is, by convention, opposite to the direction of electron flow)
A widespread misconception is that anode polarity is always positive (+). This is often incorrectly inferred from the correct fact that in all electrochemical devices negatively charged anions move towards the anode (hence their name) and/or positively charged cations move away from it. In fact anode polarity depends on the device type, and sometimes even in which mode it operates, as per the above electric current direction-based universal definition.

trollface.jpg

 

[Aindan]

I had the same issue. BUt wiki is really good at explaining!

 

[clissold]

yeah the chem kids in our physics class were mind blown too..

the teacher explained it by saying "its just like that, theres no reason"

problem solved, haha

 

[Mature Lamb]

My teacher just told us to remember anodes as sites of oxidation and cathodes as sites of reduction, rather than positive/negative terminals

 

[jamesfirst]

...?


If anode is site of oxidation in Cathode rays also, it should be negative.. lol



anyway I asked my teacher today and he told me to remember it as this:

- when emf is supplied to the circuit, cathode becomes negative.
- when it is natural process (galvanic cell), anode becomes negative

 

[hscishard]

Haven't gotten up to this stuff in phys, but I'm pretty sure that the problem is about the electron drift and conventional current flow direction. We follow electron drift in chemistry so we deal with the movement of electrons, but in physics we deal with the positive charges (so it goes opposite to electron drift) moving

 

[clissold]

how about you all just do physics, then you only have to remember that cathode is negative and anode is positive..

 

[ohexploitable]

...?


If anode is site of oxidation in Cathode rays also, it should be negative.. lol

A cathode is an electrode through which electric current flows out of a polarized electrical device.

All this shit was before they knew about the existence of electrons. The 'polarized electrical device' is the battery/power supply, in a CRT some old science dudes observed that the rays flowed out of the negative electrode (i.e. it came out of the 'polarized electrical device' though the negative end) so they called it the cathode, in galvanic cells they used to think current flowed from positive to negative (i.e. it came out of the 'polarized electrical device' though the positive end) so they called the positive end the cathode.

I think.

 

[ohexploitable]

^^

I just made all that shit up so I'm probably wrong.