The discussion about alternative sources of energy has suddenly taken center stage due to rapidly depleting fossil fuels.
There’s certainly a lot of talk about solar energy and wind energy. But it’s also equally important to understand how the source of all the renewables operate — potential energy and kinetic energy.
In this article, we’ll focus more on potential energy, including what it means, its different forms, and a few examples of potential energy. We’ll also touch on how it’s connected to gravitation and the gravitational field of Earth.
What Is Potential Energy?
Potential energy refers to the stored energy within an object that exists as a result of the object’s position, state, or arrangement. It’s one of the two primary forms of energy — the other is kinetic energy.
The stored energy is released when the position, state, or arrangement of the object changes. Very aptly named, you can think of it as the energy that has the “potential” to do some work. For instance, when you compress a spring, it has more potential energy since it can change back to its original form. But as soon as you release it, the potential energy (stored energy) is released.[1]
It was the 19th-century Scottish engineer and physicist William Rankin who first used the term potential energy. Interestingly, the term also has links to the Greek philosopher Aristotle’s concept of potentiality and actuality where he first discussed enérgeia, the source of the modern word “energy.”[2]
What Is the Definition of Potential Energy?
Live Science describes potential energy as the latent energy in an object at rest, and is one of two forms of energy.[3]
Imagine a system (we’ll call it XYZ, for the sake of example) that comprises three different parts — A, B and C. The potential energy of XYZ will be directly influenced by the relative position of A, B, and C. This is why we define potential energy as a property of a system (XYZ) instead of referring it to as the individual property of just one body or particle (A, B, and C) that forms a part of this system.
We can also associate potential energy with forces known as conservative forces.
Britannica describes conservative force as any force whose work is determined only by the final displacement of the object acted upon. The total work done by a conservative force is independent of the path resulting in a given displacement and is equal to zero when the path is a closed loop.[4]
Conservative forces ensure the total amount of work done depends on the initial and final position of the body in space.
What Does Potential Energy Mean?
According to Newton’s law about energy conservation states that the total energy in an isolated system remains constant over time.[5]
Potential energy is when an object stores energy as a result of its position, making it capable of doing more work. For instance, a stretched rubber band is loaded with potential energy.[6] Similarly, a ball, when released above the ground, will have more potential energy than after falling.
When you stretch or compress a rubber band, the kinetic energy, which is what you use to compress or stretch the band, gets converted into potential energy. And when you release the band again, the stored potential energy converts back into kinetic energy.
In other words, potential energy gets converted to kinetic energy and then back again. Moreover, the former type of energy is position relative while the latter is motion relative [7], with both representing the current state of energy.
To further explain how potential energy is part of the system, let’s continue with the raised ball example.
Here, the system comprises the Earth and the raised ball. Both of them will have more potential energy together as opposed to when they are separated further. Hence, the force of gravity between Earth and a ball is dependent on the distance separating them. When these two are separated from each other, additional energy is transferred into the system, which is then stored as gravitational potential energy.[8]
Likewise, potential energy has other forms, such as chemical energy and nuclear energy. We’ll discuss the types of potential energy in more detail later.
Where Is Potential Energy Stored?
We’ve already established that every object — whether stationary or moving — always has potential energy in some form since the latter is position relative.
The potential energy of an object refers to the object’s “potential” to do something. Let’s take the classic bow and arrow example, a favorite of physics teachers for describing kinetic and potential energy.
As soon as you draw the bow back to shoot the arrow, it will contain stored potential energy. You see, the potential energy in the archer’s arm is converted to the potential energy in the bow’s bent limbs.[9]
Its potential energy is relative to the gravitational force of the Earth in addition to the bow’s position. In fact, this applies to you as well.
Imagine yourself lying on the ground. At this moment, your body has little potential force because you’re near the Earth. But if you were suddenly suspended from the Earth’s surface at about a hundred feet, your potential energy will increase.
The higher you’re suspended from the surface of the Earth, the greater the potential energy, and the weaker the Earth‘s gravitational force.
Where Does Potential Energy Come From?
You can group different forms of energy as potential energy, with each form being associated with a specific kind of force that acts in conjunction with other physical properties of matter. This can include mass, electricity elasticity, temperature, charge — you name it.[10]
In the case of gravitational potential energy, gravitational force acts on the mass of the object. Similarly, elastic potential energy interacts with the electromagnetic force that acts on the elasticity of a deformed object, such as a stretched rubber band or a compressed spring.
Thermal potential energy works with electromagnetic force in conjugation with an object’s temperature. Chemical potential energy works with the chemical potential of a molecular or atomic configuration to act on the molecular or atomic structure of the object’s chemical substance.[11]
Let’s consider an example.
Imagine a plate is placed on a counter. If you want to raise the plate from the counter, it’s natural that you have to do some work, and energy must be used. The chemical energy that is obtained from the food you consume (which is stored in the chemicals of your body) provides you the potential energy to lift the plate while you do the work.
Now, if you assume a situation of zero energy loss, the energy supplied to lift the plate from the counter will be the same as the increase in the plate’s gravitational potential energy.
Furthermore, you can release this potential energy by simply knocking the plate off the counter. As the plate falls, the potential energy gets converted into kinetic energy. And when the plate finally hits the floor, the kinetic energy is converted into heat and sound because of the impact.[12]
How To Find Potential Energy?
Before we discuss how to find or calculate potential energy, you need to understand a few related terms: energy, work, and power.
Energy is the ability of a system or an object to do work, and it’s available in various forms ranging from mechanical energy to chemical energy to nuclear energy.[13]
When we use the word “work,” we mean the transfer of energy from one object to another. And since potential energy is converted to kinetic energy, work is also connected to kinetic energy
Power is the measurement of the energy transferred from one object to the other.
While we measure work and energy in joules, power is measured in watts. Wattage is also the measurement of heat generation, and since heat is generated any time energy is transferred, it’s an apt measurement unit.
If you’re wondering why we use the same units to measure energy and work, it’s because both concepts are the same — work is energy in motion.[14]
So, when you want to find the total energy of any object, you want to know three things related to the object:
- Its potential to do work
- Its potential to create heat
- Its potential to generate power
As a result, you have to find out the sum of the object’s mass, its distance from the Earth, electrical charge, distance from other objects, and internal elastic forces (also known as internal mechanical force).
Here’s how all of this comes together into a formula:
Potential Energy = mgh[15]
In this equation, m is the mass measured in kilograms, g is the acceleration due to gravity, and h is the height in meters
You can also use this potential energy calculator where you enter the variables, and the system will give you the answer.
What Is an Example of Potential Energy?
We’ve already discussed various examples of potential energy, but to help you understand the concept further, we’ll also enumerate a few examples with regards to its different forms.
Let’s take a quick look:
- Mechanical gravitational potential energy: A car parked at the top of a hill since it has the potential to come down the hill.
- Mechanical elastic potential energy: An archer’s bow with the string pulled back, as the pulled string has stored energy which is released once the archer lets go of the bow.
- Chemical potential energy: A charged battery, since the battery stores chemical potential energy and converts it to electrical energy.
- Electrical potential energy: A switched off light, which has a charge that’s waiting to flow through the wires.
- Magnetic potential energy: Metal spoons that respond strongly to a magnetic force.[16]
What Are the Forms of Potential Energy?
There are three forms of potential energy: elastic potential energy, gravitational potential energy, and chemical potential energy.
Elastic Potential Energy
This type of energy is stored in objects that can be either stretched or compressed. The more an object can stretch, the more elastic potential energy it will have.[17]
Gravitational Potential Energy
This form of potential energy is stored in a vertically-positioned object with the force of the Earth’s gravity trying to pull it down.
The amount of gravitational potential energy depends on the object’s weight and mass. The heavier and higher the object, the more its gravitational potential energy.[18]
Chemical Potential Energy
This energy is stored in the chemical bonds of a substance.
Different chemicals contain a large amount of chemical potential energy, which, when released, transforms some part of the energy into work and the other into heat.[19]
What Is Potential Energy Measured In?
Potential energy is measured in joules (J).[20]
Joules are the derived unit of energy. They are equal to the energy transferred to (or work done) on an object when the force of one Newton acts on the object in the same direction as that of the motion of the force through a distance of one meter or about 3 feet.[21]
Now that we’ve mentioned Newton, let’s discuss joules with the help of an item nearly synonymous with him — apples.
An apple typically weighs one Newton (about 102 grams or 0.22 pounds). When you raise an apple to the height of one meter, you perform one joule of work on it.
When you lift the apple, the potential energy of the apple changes. At its one-meter height, the apple will have one joule of potential energy. But when you release the apple, the force of gravity will come to play. It will end up performing one joule of work as the fruit drops one meter in height.[22]
Which Is an Example of Potential Energy?
Potential energy is a common phenomenon in our daily lives. From a book kept on a table to a car parked in a driveway to a switched-off cell phone — everything has potential energy.
Even renewable sources of energy utilize the concept of potential energy and kinetic energy.
While wind power converts the wind’s kinetic energy to mechanical energy before using it to generate electricity, biomass energy uses the stored chemical potential energy in the bonds of atoms and molecules that hold particles together.[23]
Potential Energy Is a Part of Our Daily Lives
We never lose energy. Instead, there’s a constant conversion that takes place — potential energy to kinetic energy and kinetic energy to potential energy.
Alternative sources of energy are being created by harnessing this phenomenon. This will help us sustain our Earth and preserve fossil fuels, while simultaneously reducing pollution.
Brought to you by justenergy.com
All images licensed from Adobe Stock.