Anode: Definition & Overview

Instructor: Joseph Marra
You likely have heard the term 'anode' when talking about a battery. In this lesson, we'll define what an anode is, how it functions as part of a system, and some easy ways for you to recall what an anode is.

What Is An Anode?

An anode is one part of a component that makes up an electric circuit. So let's start with some basics of an electric circuit so we can really understand what an anode is and how it fits into the bigger picture.

A Simple Look at Electric Circuits

Very simply, an electric circuit is a system in which electric current, which is defined as the flow of electric charge, flows through a conductor. The conductor is usually something simple like a copper wire, but can also be something more complicated like a liquid or gaseous solution, which is called an electrolyte.

But what causes the electric current? If I connected a wire end to end in a loop, would electrons flow through the wire?

The answer is no, and the reason is because with just a conductor, we don't have anything that's driving the electric charge to flow. So, how do we get electric charge to flow? We do that by adding a component to the circuit that provides what's called electric potential.

Electric potential is a simplified way of describing the potential energy an electric particle has due to its location. To really understand this principle, we can make an analogy to gravity.

Let's think of gravity very simply as an energy field. By being near the Earth, objects with mass, including ourselves, experience the effects of that gravitational energy field every day. We're pulled down towards the Earth. We have a way of quantifying those effects by calculating the energy required to get to certain physical locations in the gravitational field, and it's the equation for potential energy (PE), which is:

PE = m*g*h (Equation 1)

where m is the mass of the object, g is the acceleration due to gravity of an object, and h is the height of the object.

So, what does this equation tell us? It tells us that if we, with our mass (m), are at a certain height (h), we'll have a certain amount of potential energy (PE). Another way of thinking about this is that if you want to get yourself with your mass to a certain height, something has to provide the required amount of energy to get you there. Think of it like climbing a mountain - if you're at the top, you put in a lot of energy to get there because you fought the gravitational field of the Earth all the way up!

Electric potential is a lot like gravitational potential. It describes the amount of energy a particle has based on its location. It's a way of quantifying how much energy the particle was given to make it move against an electric field. In the case of our electric circuit, that field is the field created by the repulsion of the electric particle to other like particles. So, just like our mountain climbing situation, we're describing a particle that pushed its way through an electric field to get to where it is!

How Anodes Fit Into An Electric Circuit

How does this relate to an anode? An anode is one part of a device in an electric circuit in which electrons build up and leave through the conductor.

Let's talk about a very specific example that we're all probably familiar with - a battery.

A battery works by housing an electrolytic solution and two conductors at each end, as shown in the Figure 1 below. For our purposes, we'll say that the bottom end is the anode and the top end is the anode's opposite, which we call the cathode.

Anode 1 - Battery with + and -

A chemical reaction inside of the battery causes electrons, which are negatively charged, to gather at the anode, and protons, which are positively charged, to gather at the cathode, as shown in Figure 2 below:

Anode 2 - Battery showing charge

As you can see, we're getting closer to having all the components we need for our electric circuit. The electrolyte in the battery creates an electric potential difference and a driving force for current to flow. All we need to do is connect the two ends of the battery, and we'll have electrons flow from the anode to the cathode, as you see in Figure 3 below:

Anode 3 - Battery with conductor connected

Now that we've got our electric circuit set up, we can really understand what the anode is.

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