# Electric Potential: Charge Collections and Volt Unit

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• 0:07 Electric Charge and…
• 0:40 Charge Collections and Voltage
• 2:19 The Effect of Charge Density
• 3:10 Units of Voltage
• 3:48 Lesson Summary

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Lesson Transcript
Instructor: Jim Heald

Jim has taught undergraduate engineering courses and has a master's degree in mechanical engineering.

In this lesson, we'll find out that electric charges can be rather lazy until something motivates them to get work done. Find out what gives electric charges the potential to do work and how we measure that potential with something called voltage.

## Electric Charge and the Potential to Do Work

Have you ever had one of those days when you just didn't feel motivated to do much of anything? Or how about a time when the pressure of a looming deadline pushed you to get a whole lot of work done in a short period of time? Sometimes you have a lot of potential to do your work, and other times not so much. Interestingly enough, charged particles are just like you. In this lesson, we're going to look at what motivates charged particles to do work and how we measure their potential to do that work.

## Charge Collections and Voltage

When a charged particle sits around all by itself, it doesn't have any motivation to do work. You see, the potential to do work is not an inherent property of charged particles but rather the result of the forces exerted by other nearby charged particles. When we gather a group of charged particles together, it's called a charge collection. The most common example of a charge collection is a battery, which is simply a bunch of electrons packed into a tight space. Because the electrons all have the same negative charge, they are all very motivated to get out of the battery, and this is what gives rise to a thing called voltage. Voltage is a measure of the amount of work that a group of charged particles will do if allowed to flow in an electric circuit. In a way, you can think of voltage as a measure of how motivated the electrically charged particles are to get out and do something.

A convenient analogy to help us understand voltage is water pressure in a pipe. A battery always has voltage, whether it's powering a toy or sitting in the drawer doing absolutely nothing. This is just like the pipes in your bathroom, which have pressure regardless of whether you're taking a shower or not using the water at all. Another similarity is that voltage indicates how much work the charged particles will do when they flow out of the battery. Higher voltage means more work. This is similar to the way a high-pressure power washer will clean more bugs off your windshield than a low-pressure garden hose.

## The Effect of Charge Density

The voltage of a battery, or of any other charge collection, is dependent only on how tightly the charged particles are packed together. This is called charge density. The closer the particles are to each other, the more they repel each other, which gives them more motivation to go out and do work. Interestingly, voltage is independent of the total number of charged particles in the collection. We can see this with different sizes of batteries. Triple-A batteries have the same voltage as D-size batteries because they have the same charge density. This means that an electron from the triple-A battery will do the same amount of work as an electron from the D-size battery. The only difference is that the larger D-size battery will last longer because it contains more electrons.

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