anode is it positive or negetive

[SilverFox]

Hello Rjspeers,

Welcome to CPF.

When measuring a cell the anode is the + end. Your assumption is correct.

Tom

 

[Mr Happy]

Hello Rjspeers,

Welcome to CPF.

When measuring a cell the anode is the + end. Your assumption is correct.

Tom

Hi Tom,

I was going to answer this earlier, but then the forum stopped responding and I couldn't post.

However, I rather thought the anode of a battery is by convention the negative electrode and the cathode is the positive. All the references I find say this.

(And if in doubt it is best to avoid the anode and cathode labels altogether and just refer to the positive and negative electrodes. This will avoid any confusion with electrical engineers, chemical engineers, physicists, chemists, or anyone else... )

 

[samgab]

Yes, MH is right...

Confirmed by the source of all correct and indisputable info - Wikipedia: ( )

• In a discharging battery or galvanic cell (diagram at right) the anode is the negative terminal since that is where the current flows into the device (see drawing). This inward current is carried externally by electrons moving outwards, negative charge moving one way constituting positive current flowing the other way. It is continued internally by positive ions flowing into the electrolyte from the anode, i.e., away (surprisingly) from the more negative electrode and towards the more positive one (chemical energy is responsible for this "uphill" motion).
• In a recharging battery, or an electrolytic cell, the anode is the positive terminal, which receives current from an external generator. The current through a recharging battery is opposite to the direction of current during discharge; In other words, the electrode which was the cathode during battery discharge becomes the anode while the battery is recharging.

So as per the question, if you touch the probes of a DMM to an open circuit cell, the "+" terminal will be the cathode and the "-" will be the anode, right?

 

[sxl168]

Technically this is correct as a tiny amount of current is needed to be drawn from the cell in order for the DMM to read the voltage, however I would refer to SilverFox's post as the consensus opinion on labeling. The way I was always taught for this is that the electrode that generates anions (+ ions) is the anode and the electrode that generates cations (- ions) is the cathode in an electrochemical cell. The electrode designation obviously reverses depending on if you are charging or discharging a cell, but the polarity (+ and - terminal designations) of a cell does not change with charge or discharge, even though readings may go negative with cell over-discharge. The + and - terminal designations are reference points and are unvarying, the same fashion that a grounding point is designated as 0 Volts.

 

[Mr Happy]

The way I was always taught for this is that the electrode that generates anions (+ ions) is the anode and the electrode that generates cations (- ions) is the cathode in an electrochemical cell.

Let us apply this statement to a battery. When you connect a load like a voltmeter to a battery then electrons flow out of the negative electrode, through the voltmeter, and into the positive electrode. After the electrons flow into the positive electrode they combine with molecules in the electrolyte and cause negative ions to leave the electrode in solution. The positive electrode in a battery is therefore generating cations, and is consequently the cathode. It follows that in a battery the positive electrode is the cathode and the negative electrode is the anode.

 

[MagPap]

The way I was always taught for this is that the electrode that generates anions (+ ions) is the anode and the electrode that generates cations (- ions) is the cathode in an electrochemical cell. The electrode designation obviously reverses depending on if you are charging or discharging a cell, but the polarity (+ and - terminal designations) of a cell does not change with charge or discharge, even though readings may go negative with cell over-discharge. The + and - terminal designations are reference points and are unvarying, the same fashion that a grounding point is designated as 0 Volts.

Just a little correction for better undestanding. The positive +ions are the cations, and the negative -ions are the anions.

 

[sxl168]

After looking that up, I can't believe I had that backwards all these years. You are right about that and also you need to modify "the electrode that generates" to "the electrode that receives" in the post also.

 

[SilverFox]

In my defense, I read this question

If you hook up a DC voltmeter with the red lead plugged into the meters positive socket and the black lead plugged into the negative socket then put the test leads across the terminals of a battery if the voltage reads positive am I to assume that the red lead is on the anode? I realize that current direction is the determining factor but would this not be reflected in the voltmeter reading?

as trying to figure out which way to put batteries into a device and determining that by using a voltmeter. When you put the red + lead of the voltmeter on the + end of the battery and the black - lead of the voltmeter on the - end of the battery, you will read a positive voltage.

The question of which way the current flows is not important if you put the battery in backward and blow the device up...

Tom

 

[MagPap]

After looking that up, I can't believe I had that backwards all these years. You are right about that and also you need to modify "the electrode that generates" to "the electrode that receives" in the post also.

We can rewrite it: the electrode that receives anions (- ions) is the anode. Then, in an electrolytic cell, the anode is the positive terminal. ( the positive attract the anions' negative charge).

It has been explained better before:

or rechargeables: It operates as a galvanic cell during discharge and as an electrolytic cell during charge. As a consequence, the anode is the negative electrode during discharge, while it is the positive electrode during charge; at the same time, the cathode is the positive electrode during discharge, while it is the negative electrode during charge. This can create a confusing situation, and it is preferable to refer to the electrodes of a rechargeable battery as "positive" and "negative," because this designation is independent of the operational mode. Unfortunately, this nomenclature is not always followed. Often the "negative" electrode is designated as anode and the "positive" electrode is designated as cathode. This naming convention is a carry-over from the convention of the non-rechargeable battery.

 

[45/70]

Once again, I find myself wondering how so much discussion can erupt over such a simple question LOL.

As far as a battery cell is concerned, the positive (+) and negative (-) poles are just that, and do not ever change, as has already been explained. As for anode and cathode, this is dependent on the direction of the flow of current. Is the battery, or cell being charged, or is it being discharged? Between these two conditions, the anode and cathode are reversed, again as has already been explained.:shrug:

Dave

 

[Jackasper]

WOW, I learn something everyday.

 

[samgab]

Here's an accurate and informative video that will help.
Not only explains what anode and cathode really are, but gives great battery charging advice

WARNING: This is a spoof! oo:

 

[InHisName]

It's called electrical tape because it conducts electricity.
WOW! So slickly done and professional 'quality'. THEN he pops with that! comment.
Totally ruins his credibility.

 

[samgab]

It's called electrical tape because it conducts electricity.
WOW! So slickly done and professional 'quality'. THEN he pops with that! comment.
Totally ruins his credibility.

Yeah, I loved that bit. All part of the fun. I'm sure some people are taken in by his videos. Genius!

 

[45/70]

Yeah, I loved that bit. All part of the fun. I'm sure some people are taken in by his videos. Genius!

Hi Sam. You should probably indicate somewhere in that post, that it's a spoof. There are enough folks who are new to rechargeable batteries that are confused enough already. It's not because they're unintelligent or anything, they just don't have any experience.

I agree that the vid is done very well (the music especially cracks me up), but I'm afraid it may steer someone in the wrong direction. We have newcomers wanting to charge eneloops in Li-Ion chargers, and vice versa. Compared to that, a misleading video about how to charge alkaline cells is nothing.

Just a thought.

Dave

 

[samgab]

Hi Sam. You should probably indicate somewhere in that post, that it's a spoof. There are enough folks who are new to rechargeable batteries that are confused enough already. It's not because they're unintelligent or anything, they just don't have any experience.

I agree that the vid is done very well (the music especially cracks me up), but I'm afraid it may steer someone in the wrong direction. We have newcomers wanting to charge eneloops in Li-Ion chargers, and vice versa. Compared to that, a misleading video about how to charge alkaline cells is nothing.

Just a thought.

Dave

lol, done. I hoped the would imply that without being super obvious, but you're right, it's just borderline enough that a noob might go taping their alkaline cells up hoping to charge them. Of course no harm would befall them. But no benefit either.
Did you see how he'd taped the 2 D cells onto the corner of the 9V array at the end?

 

[MarioJP]

LOL'ed at the video.