Potential Difference: Definition, Formula & Examples

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  • 0:02 What is Electric Potential?
  • 2:58 Electric Potential Difference
  • 4:34 Some Simple Examples
  • 5:21 Lesson Summary
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Lesson Transcript
Instructor: Joseph Marra
Electrical potential difference is the difference in the amount of potential energy a particle has due to its position between two locations in an electric field. This important concept provides the basis for understanding electric circuits.

?!!!What Is Electric Potential?

In order to understand electrical potential difference, we need to first understand what electric potential is. The best way of doing that is through an analogy to a concept that you should be familiar with: gravitational potential energy.

Electric potential is a simple way of quantifying the potential energy that an electric particle has as a result of its location in an electric field. This is similar to how we talk about objects with mass and their potential energy as a result of their location in a gravitational field.

As a result of being within the Earth's gravitational field, objects that have mass experience the effects of that gravitational energy field - the effect they feel is that they are being pulled down with some force that is proportional to their mass and their location in that field. Does this mean that we can say that we can plainly describe locations in the Earth's gravitational field as inherently high potential energy locations? No, not necessarily. Why not? Because the potential energy that an object has depends not only on its location in the gravitational energy field, but also on its mass.

For example, a space shuttle 10,000 feet above the surface of the Earth has much more potential energy than a molecule of air the same height above the surface of the Earth. They're both at the same location in the gravitational field, but their potential energy is very different because their mass is very different. What we can do, though, is define each location as the amount of potential energy per unit mass required to achieve that location. This allows us to level the playing field and compare locations by the energy required to get to them. It makes the potential energy that an object has purely a function of its location. We call this gravitational potential, and it's defined as the amount of potential energy an object has in a gravitational field per unit mass.

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 away from other particles. So, just like an object moved through our gravitational field, we're describing a particle that pushed its way through an electric field to get to where it is. And, just like how we 'leveled the playing field' by describing locations in the gravitational field as the amount of energy per unit mass to get there, we describe electric potential as the amount of energy required for a charged particle to achieve a location in an electric field of known strength. Again, it makes the electric potential that an object has purely a function of its location.

Electric Potential Difference

Now that we've spent some time understanding what electric potential is, we can really understand what electric potential difference is.

Consider two points in an electric field. Notice that point A is much closer to the source of the electric field than point B.

Electric potential difference

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