# Help with the conventions used for curl operator

• ppoonamk
In summary, the conversation is about a person trying to understand the derivation of curl on the given website. They are confused about the notation and why the line integral is taken in the Δz direction when the change is in the y direction. The expert explains that the component Ay is integrated left-to-right along the bottom of the square and also along the top of the square from right-to-left, and that the person has now understood the explanation.

#### ppoonamk

http://web.mit.edu/6.013_book/www/chapter2/2.4.html

I was going through the curl derivation on the above link. How does equation 3 turn out? Δy is the incremental length. But how do you decide whether it is +Δy/2 or -Δy/2. And why is the line integral taken Δz when the change is in the y direction. I am utterly confused :(

ppoonamk said:
http://web.mit.edu/6.013_book/www/chapter2/2.4.html

I was going through the curl derivation on the above link. How does equation 3 turn out? Δy is the incremental length. But how do you decide whether it is +Δy/2 or -Δy/2. And why is the line integral taken Δz when the change is in the y direction. I am utterly confused :(

The component Ay is integrated left-to-right along the bottom of the square (where z = -Δz/2, and y goes from -Δy/2 to +Δy/2), and also along the top of the square from right-to-left.

RGV