Cathode and Anode - General Awareness for SSC CGL PDF Download

Electrodes: Anode and Cathode

An electrode serves as a conductor that allows electric current to enter or exit an electrolyte in an electrolytic cell. These electrodes are categorized into two primary types: the anode and the cathode. At the anode, oxidation takes place, with electrons exiting the electrolyte. Conversely, at the cathode, reduction happens, and electrons enter the electrolyte. The movement of electrons from the anode to the cathode generates an electric current.

Cathode

In an electrochemical cell, the cathode is the electrode where reduction reactions occur. Here, atoms or molecules acquire electrons, leading to the creation of negatively charged ions or neutral compounds. Typically, the cathode connects to the negative terminal of the power supply.

As part of a chemical process, electrons travel from the anode—where oxidation occurs—to the cathode, establishing a current flow. The cathode hosts the reduction segment of a redox reaction, which entails reactants accepting electrons.

Examples of Cathodes

Cathodes appear in various electrochemical setups, such as:

• In a conventional dry cell battery, the carbon rod functions as the cathode.
• During electrolysis, the electrode producing hydrogen gas serves as the cathode.
• In a mercury vapor lamp, the cathode releases electrons to ionize the mercury vapor within the bulb.
• In a cathode ray tube (CRT) used for displays, the electron gun, which directs and speeds up electrons toward the phosphor-coated screen, operates as the cathode.

Anode

The anode in an electrochemical cell is the electrode where oxidation reactions take place. It is the point where electrons depart from the device into the external circuit, causing the anode material to lose electrons and develop a positive charge.

In a galvanic (voltaic) cell, the anode is the positive terminal, whereas in an electrolytic cell, it is the negative one. Within a basic galvanic cell, oxidation of the anode material releases electrons. In electrolytic cells, however, the anode delivers electrons to the electrolyte.

Examples of Anodes

Anodes are integral to numerous electrochemical systems, including:

• In a standard zinc-carbon dry cell battery, the zinc casing serves as the anode, paired with the carbon rod as the cathode.
• In lithium-ion batteries, common anode materials include lithium cobalt oxide (LiCoO₂), lithium manganese oxide (LiMn₂O₄), or lithium iron phosphate (LiFePO₄).
• In lead-acid batteries, the anode consists of lead.
• During electrorefining, the anode is the impure metal that dissolves in the electrolyte, releasing electrons as it corrodes, while purified metal plates onto the cathode.

Difference between Anode and Cathode

The primary distinctions between anodes and cathodes in electrochemical cells are outlined in the table below:

Common Misconceptions About Cathode and Anode