Differences
This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision | ||
184_notes:gradient [2020/09/22 15:59] – dmcpadden | 184_notes:gradient [2021/02/23 20:18] (current) – bartonmo | ||
---|---|---|---|
Line 3: | Line 3: | ||
==== What is a gradient? ==== | ==== What is a gradient? ==== | ||
+ | [{{ 184_notes: | ||
+ | |||
A gradient is simply a change in the amount of something. For example, you may have seen a color gradient (like the one shown at the right), where you start with a single color that slowly fades to white. In this case, the color is what is changing, so we call it a "color gradient." | A gradient is simply a change in the amount of something. For example, you may have seen a color gradient (like the one shown at the right), where you start with a single color that slowly fades to white. In this case, the color is what is changing, so we call it a "color gradient." | ||
Line 8: | Line 10: | ||
It would be impossible to actually count or draw every single electron along the surface of a wire. There are simply too many, and it would make our picture too messy to be useful. Instead, we draw a small representative amount of charges on our picture. For example, if we go back to the picture with the battery and surface charges: | It would be impossible to actually count or draw every single electron along the surface of a wire. There are simply too many, and it would make our picture too messy to be useful. Instead, we draw a small representative amount of charges on our picture. For example, if we go back to the picture with the battery and surface charges: | ||
- | [{{ 184_notes: | + | [{{ 184_notes: |
There are a few things to notice: | There are a few things to notice: | ||
- We have drawn a small amount of charges on the surface of the wire. For example, in the top right corner, we have drawn a total of eight negative signs on the outside of the wire. This does not mean that there is exactly eight electrons on the wire. Instead, **this just shows that we expect this area of the wire to have a large concentration of negative charge**. There is no particular reason why we drew eight - we could have picked 12 or 6 or any other number to start with. The important part is that there are more negative signs in this area than any other part of the wire. | - We have drawn a small amount of charges on the surface of the wire. For example, in the top right corner, we have drawn a total of eight negative signs on the outside of the wire. This does not mean that there is exactly eight electrons on the wire. Instead, **this just shows that we expect this area of the wire to have a large concentration of negative charge**. There is no particular reason why we drew eight - we could have picked 12 or 6 or any other number to start with. The important part is that there are more negative signs in this area than any other part of the wire. | ||
- | - As we move along the wire on the right side, the number of negative decreases from 8 to 6 to 4 to 2. **This represents the gradient of surface charges.** As we move along the wire, we expect there to be a lot of negative surface charges near the battery, and as you get further away along the wire, there should be fewer and fewer negative surface charges. Remember, the //change// in the amount of charge is what makes it a gradient. Similarly, as we approach the positive side of the battery, we draw 2 to 4 to 6 to 8 positive signs to represent the increase in the amount of positive surface charges. | + | - As we move along the wire on the right side, the number of negative |
+ | - The last thing to notice here is the electric field arrows. We said already that the gradient is what creates the electric field field. **This means that the electric field arrows need to match your surface charge gradient and vice versa**. Remember from [[184_notes: | ||
+ | |||
+ | In the next page of notes, we'll talk more about how the surface charge gradient and electric field create a current in the wire. | ||