- #1

- 465

- 4

$$W=\frac{ε}{2}\int{\vec{∇}\cdot\vec{E})Vdτ}$$

where ε is a constant, E= -∇V, τ is a volume element

how do i end up with the following via integration by parts?

$$W=\frac{ε}{2}[-\int{\vec{E}\cdot(\vec{∇}V)dτ}+\oint{V\vec{E}\cdot d\vec{a}}$$]

where the vector a is an area element

thanks