Danielle has taught middle school science and has a doctorate degree in Environmental Health
Definition and Background
Before you read this lesson, grab a non-rechargeable battery. If you don't have one, don't panic, you can just follow along using this image.
As you look at the battery, you will notice it has two ends. That is, there is a positive sign on one end and a negative sign on the other end. Did you know these signs are representative of two different types of electrodes, an anode, and cathode? Before we continue dissecting our battery, let's discuss more about this term 'electrode' in more detail.
Electrode refers to a conductor by which electrical currents can travel. In fact, these little guys are sometimes referred to as electrical conductors. You can find them in a wide variety of electrical devices such as batteries, electrolytic cells, or electron tubes.
You might be wondering what is an electrode made of. Well, what do you suspect is a great conductor of electricity? Metals are great conductors of electricity. In fact, metals are commonly used in the production of electrodes. The type of metals used range from copper to zinc to gold and platinum.
Think of an electrode as a bridge that forges a passageway for electrons to travel on. Electrons are the guys zipping around the nucleus of an atom. Technically, they're subatomic particles with a negative electric charge.
Atoms have protons too, which have a positive charge. Atoms with the same number of protons and electrons are called neutral, because their charges cancel each other out.
However, if the number of electrons are different from the proton count, the atom will either be negative or positive. We can call that atom an ion. There are two different types of ions:
- Cations are positively charged ions.
- Anions are negatively charged ions.
Anodes and Cathodes
Similarly, there are two different types of electrodes:
- An anode is an electrode that attracts anions.
- A cathode is an electrode that attracts cations.
A helpful way to remember the relationship between ions and electrodes is to know that 'cat' in cathode refers to cation. The first letter 'a' in anode refers to anion.
When you connect both electrodes together, you can form an electrical circuit. An electrical circuit is the path by which electrons flow. Thus, if the electrode is our bridge that electrons travel on, the circuit is the road map electrons use to determine where to travel. In electrical devices, electrons will always flow from the anode to the cathode.
How Does an Electrode Work?
In describing how an electrode works, there are two different electrical devices we can use as examples. The first example involves our battery. As shown in this diagram, a battery has two terminal ends, the cathode and anode. Two different processes occurring inside the battery contribute to the flow of electrical current. First, chemical reactions are firing off within the battery. Second, we have electrons zooming around from the anode and cathode to generate electricity for a device.
Let's say you'd like to power a flashlight. When you place the battery in its holder, chemical reactions take place. These reactions release a lot of ions at the anode. As the ions dissolve they leave their electrons behind at the anode.
Building up at the anode, the electrons are not happy. They would rather leave this cramped space than huddle close together. In order to do so they travel to the site of the battery with available occupancy, the cathode. By traveling from the anode to the cathode, in a circuit, light can be produced in our flashlight. But what happens if we remove the battery? If the battery is removed, our power source used to drive the chemical reactions creating this electron flow comes to an end. The end result is a flashlight with no light.
In this diagram, we can also view a similar process in electrolytic cells. An electrolytic cell is a device used to convert chemical energy to electrical energy. One use of an electrolytic cell is in electrometallurgy to remove precious metals from mineral ores.
The major difference between a battery versus the electrolytic cell is that the electrode is immersed in a solution. The cations and ions, floating in this solution, are called electrolytes. Did you notice the power supply in the cell? This power source works to move electrons through the solution from anode to cathode. As electrons move this causes a current to flow in the solution.
Whether an electrical current is generated in a battery or constructed electrolytic cell, electrodes allow any current to flow.
Electrodes are conductors by which electrons flow through to generate a current. There are two types of electrodes, cathodes, and anodes. Cathode attracts the positively charged cations. Anode attracts negatively charged anions.
Electrodes are commonly made of metals such as platinum and zinc. As great conductors of electricity, they're found in electrical devices such as batteries and electrolytic cells. Electrons flowing from the negative end of the electrode, or anode, to the positive end, or cathode, mean an electrical current can be generated.
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