An anode is an electrode where the oxidation reaction takes place or we can also define it as the terminal in which current flows into a device from outside. While reduction takes place at the cathode and the conventional current flows out of the device through this terminal. In this article, we will see the actual difference between anode and cathode.
Before learning about anode and cathode we need to understand what an electrode is. An electrode is a substance that helps in the conduction of electricity wherein the current enters or leaves the non-metallic medium like an electrolyte. It is an eminent component of an electrochemical cell that remains in contact with the electrolyte.
Anode vs Cathode
Let’s see the key differences between anode and cathode through the following table.
| Basis of Comparison | Anode | Cathode |
| Type of reaction taking place at the electrode | Oxidation reaction takes place at the anode. | Reduction reaction occurs at the cathode. |
| Movement of Electrons | Electrons flow out of the anode. | Electrons flow into the cathode. |
| Polarity of the terminals in an electrolytic cell | Positive | Negative |
| Polarity of the terminals in a galvanic cell | Negative | Positive |
| Attraction of cations or anions | The anode attracts anions in an electrolytic cell. | Cathode attracts cations in an electrolytic cell. |
What is anode?
The electrode at which oxidation reaction takes place is known as the anode. It can also be defined as the electrode from which the current enters into the polarized electrical device. An anode is a terminal where current flows into a device from the outside. We can’t define an anode as positive or negative because its polarity depends upon the type of cell being used.
During discharging of a battery or we may say that when a load is connected to the battery, the electricity flows from the positive terminal of the battery to the negative terminal of the battery. So in this case anode will be the negative terminal because electricity flows into the negative terminal.
During charging of the battery, the electricity flows from the negative terminal of the battery to the positive terminal of the battery. So in this case, the anode will be the positive terminal of the battery.
In the case of capacitors and diodes, the anode is that side where we connect the positive terminal, this is because current will enter from this side. And the side where we will connect the negative terminal will be the cathode.
It is not mandatory that cathode and anode will always be used together, there are applications where anode alone is used. In the sacrificial anode coating, zinc is used to protect metals. This method is common in ships where a static charge is created due to the flow of water. The sacrificial anode which we have used will absorb all the static charge and slowly gets disintegrated. In this way, we can protect the metal. Only the coating needs to be restored.
What is cathode?
A cathode is an electrode from where the current flows out of the device. Since the direction of flow of electrons is opposite to the direction of the current, we can say that a cathode is an electrode that has the flow of negatively charged electrons entering into it.
It is the electrode at which a reduction reaction takes place. Just like anode, there is no particular polarity of a cathode, it also depends on the type of cell being used.
During discharging of a battery or, when an external load is connected to the battery, the electric current flows from the positive terminal of the battery to the negative terminal of the battery. Since the current is leaving from the positive terminal of the battery, it (positive terminal) will act as a cathode during the discharging condition
During charging condition electric current flows from the negative terminal of the battery to the positive terminal of the battery. In this case, an electric current is leaving from the negative terminal of the battery so it (negative terminal) will act as a cathode.
The cathode attracts cations and oxidizes them in electrolytic and galvanic cells. In X-ray tubes and, electron guns, the part that emits electrons into the device forms the cathode.
A cathode can be a hot cathode or a cold cathode. A hot cathode is one that is heated in the presence of a filament to emit the electrons by thermionic emission. Cold cathodes are not heated by any filament.
Conclusion
Cathode and anode are two important types of electrodes in an electrical cell and helps to understand what and where electrochemical reactions are taking place. An important thing to note here is that there is no certain polarity assigned to a particular electrode, for example, we can’t say that anode will be of positive polarity or negative polarity, it depends on the type of cell being used.
In the case of a galvanic cell, the anode is of negative polarity and the electrons move toward the external part of the circuit. While in the case of electrolytic cells the anode is of positive polarity. The two electrodes i.e. cathode and anode can also be used to separate compounds into constituent ions or molecules through the process of electrolysis.
Author
Deepak Yadav
Aligarh Muslim University, Aligarh
