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Here's a look at the difference between the anode and cathode of a cell or battery and how you can remember which is which.

Flow of Current

The anode and cathode are defined by the flow of current. In the general sense, current refers to any movement of electrical charge. However, you should keep in mind the convention that current direction is according to where a positive charge would move, not a negative charge. So, if electrons do the actual moving in a cell, then current runs the opposite direction. Why is it defined this way? Who knows, but that's the standard. Current flows in the same direction as positive charge carriers, for example, when position ions carry the charge. Current flows opposite the direction of negative charge carriers, such as electrons in metals.

Cathode

  • The cathode is the negatively charged electrode.
  • The cathode attracts cations or positive charge.
  • The cathode is the source of electrons or an electron donor. It may accept positive charge.
  • Because the cathode may generate electrons, which typically are the electrical species doing the actual movement, it may be said that cathodes generate charge or that current moves from the cathode to the anode. This can be confusing, because the direction of current would be defined by the way a positive charge would move. Just remember, any movement of charged particles is current.

Anode

  • The anode is the positively charged electrode.
  • The anode attracts electrons or anions.
  • The anode may be a source of positive charge or an electron acceptor.

Cathode and Anode

Remember, charge can flow either from positive to negative or from negative to positive! Because of this, the anode could be positively charged or negatively charged, depending on the situation. The same is true for the cathode.

Keeping Them Straight

Remember the cathode attracts cations or the cathode attracts + charge. The anode attracts negative charge.

Electrochemical Cells | Galvanic Cell Example Problem

Comments

December 5, 2011 at 7:37 am
(1) John D'Errico says:

Well, you got me. I thought I knew about the flow and the direction of current, but that’s gone now. This explanation was the same as explanations about the north and south poles of a magnet or the north and south seeking ends of a compass needle. It’s the north-seeking end, which means it’s really the south pole because the south pole is attracted to the north pole which is really the south pole until the earth reverses it’s magnetic poles; then the south pole will become the south pole of the north pole and the north pole will fall off the earth. Good lord!

December 6, 2011 at 12:10 am
(2) jon congdon says:

In a wet cell the oxidation occurs at the anode; correct? And reduction occurs at the cathode. If so, the more active metal is at the anode and the less active metal is the cathode. So the electrons are produced or originate from the anode at the same time that positive ions of the more active metal are released into the solution. The electrons then travel through a conductive wire to the less active metal while positive ions flow into solution. The anode is then sacrificed in the process. At the cathode positive ions in solution join with electrons that are in excess there and form nuetral metal atoms. Thus the cathode grows in mass as the anode decreases.

December 7, 2011 at 12:36 am
(3) annette says:

Always the electrode having the greater reduction potential is the cathode and the electrode having lesser reduction potential is the anode.

January 16, 2013 at 12:31 pm
(4) Jason says:

Are you sure about your definitions. I’m looking for some clarifications about terminology as I teach a high school electrochemistry unit and most resources I’ve consulted (textbook, online printed notes, wikipedia, the electrochemical cells page here at about.com) say oxidation happens at the anode thus supplying the circuit with electrons and being labelled negative, while the cathode receives electrons from the circuit and uses them to reduce the solution and is referred to as the positive electrode. While the convention for current is to say that it flows “against the stream” of electrons from + to -, this is the only resource that I’ve come across that relabels the electrodes. Can you cite some sources that back your article or make the appropriate corrections?

January 6, 2014 at 10:04 pm
(5) Rafael Jimenez says:

I agree Jason, I had learned that the definitions were opposite and so far I have done a quick review and the anode is the sacrificial metal and thus looses material as well as electron that flow towards the cathode. The cathode being the acceptor of electrons and thus were reduction happens and cations are usually converted into material.

March 4, 2014 at 3:59 am
(6) wajahat hussain says:

thanks it is helpful.

March 12, 2014 at 12:43 pm
(7) Matthew Meier says:

Hello Jason, and others thrown off by the above article. I can try to clarify for those confused in the comments section. The answer here is a difference of convention.
Physicists look at a “discharging battery” so to speak, while biochemists look at a charged capacitor.
-Oxidation occurs at the Anode (Electrons are lost from the anode)
-Reduction occurs at the Cathode (electrons are gained by the Cathode)
So in physics, we look at electron flow in circuit, (technically current is the imaginary flow of a theoretical positive). Since the electrons move away from the Anode towards the Cathode (becuse Oxidation is LOSS), physicists call the Anode negative (repels electrons, or attracts the theoretical reverse positive current.). So physics circuit: Anode = -, Cathode = + because of where ELECTRONS go.

Biochemists look at a capacitor plate charged such as in gel electrophoresis. In this case we are not concerned with the internal flow of electrons in the circuit, but what type of free ions the capacitor attracts. Sine the Anode is the site of Oxidation (Loss of e-) over time it becomes positive on the surface, attracting Anions (- ions). So in biochem: Anode=+ and the Cathode= – because of where IONS go.

The simple explanation for students I tutor:
Cathodes have positive core and a negative surface charge
Anodes have a negative core and a positive surface charge

Electrons care about the core, while Ions care about he surface

April 3, 2014 at 7:41 pm
(8) cliff sondrup says:

Yes. Just think if the charge has been induced on the object or not. (i.e. a capacitor or a battery) Meaning the electrons that the object had to begin with can be drawn up (something indicating an anode, that is, being a source of electrons). Even if the electrons are all drawn up, what counts is the infinitismal time when the circuit is made. Where did the electrons come from RIGHT AWAY. this thinking will give you the correct answer whether you are a chemist or otherwise. Asking where an electron will go in a capacitor will not get you the correct answer.

In short: where did the electrons come from INITIALLY with connection of the circuit. This is the Anode.

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