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Meir Achuz
Meir Achuz is offline
Feb28-13, 09:30 AM
Sci Advisor
HW Helper
P: 1,937
The first two terms of Eq. (4) should be
[tex]\mathbf{f} = \epsilon_0\left[ \boldsymbol{\nabla}\cdot( \mathbf{E}\mathbf{E}) + (\mathbf{E}\cdot\boldsymbol{\nabla}) \mathbf{E} \right][/tex].
Then use [tex](\mathbf{E}\cdot\boldsymbol{\nabla}) \mathbf{E}
=(1/2)\nabla({\bf E\cdot E })[/tex].
Writing these two terms with indices gives Eq. (5).
The other terms don't enter with no B field. dE/dt can't enter because this would imply a B field.