# Field Angular Momentum (Thomson Dipole)

by Septim
Tags: angular momentum, electrodynamics, griffiths
 P: 119 1. The problem statement, all variables and given/known data I have attached the question as jpg to this post. Typing these were too time consuming and I uploaded the relevant sections as image files, thanks for your understanding. 2. Relevant equations mu_0*epsilon_0*Poynting Vector = Momentum density Position vector X Momentum density = Angular momentum density 3. The attempt at a solution These too are attached in png format. I have found out that angular momentum density has two components, one in the z direction and one in the x direction. According to the books solution the x component integrates to zero but I was unable to verify this and I am highly skeptical about this topic. Any help would be appreciated. I have attached the relevant information to this post. 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution Attached Thumbnails
 PF Patron HW Helper Thanks P: 3,763 In constructing your equation (8), note that ##\hat{r}## will generally have a ##\hat{y}## component as well as ##\hat{x}## and ##\hat{z}## components: ##\hat{r} = (\hat{r} \cdot \hat{x}) \hat{x} + (\hat{r} \cdot \hat{y}) \hat{y} + (\hat{r} \cdot \hat{z}) \hat{z}##. ##\hat{r} \cdot \hat{x} = sin\theta cos\phi##, etc. See what you get for the x and y components of the angular momentum when you integrate over ##\phi##.

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