- #1
Shinobii
- 34
- 0
The angular momentum of the electromagnetic field is defined as,
$$
\vec{L_{em}} = \int \vec{l_{em}} d^3r.
$$
To solve this for a rotating sphere I must consider the cases where r < R and r > R.
When I did this problem I thought that there would be two solutions, one for both cases; however, it turns out that there is one solution,
$$
\vec{L_{em}} = \int \vec{l_{em}}_{(r<R)} \, d^3r + \int \vec{l_{em}}_{(r>R)} \, d^3r.
$$
Can anyone tell me why that is? Conceptually I do not understand what is going here.
$$
\vec{L_{em}} = \int \vec{l_{em}} d^3r.
$$
To solve this for a rotating sphere I must consider the cases where r < R and r > R.
When I did this problem I thought that there would be two solutions, one for both cases; however, it turns out that there is one solution,
$$
\vec{L_{em}} = \int \vec{l_{em}}_{(r<R)} \, d^3r + \int \vec{l_{em}}_{(r>R)} \, d^3r.
$$
Can anyone tell me why that is? Conceptually I do not understand what is going here.