# Simple calculation about Magnetic induction

1. May 10, 2017

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Why does the second term become zero??

2. May 10, 2017

### kuruman

Because it does not exist. If, in the previous equation, you substitute the gradient with some vector $\vec{V} = \vec{\nabla} \left ( \frac{1}{|\vec{x}-\vec{x}'|} \right )$, you will see why. There is no vector identity in the front of the book to be used.

3. May 12, 2017

### vela

Staff Emeritus
The derivative $\nabla$ is with respect to $\vec{x}$, not $\vec{x}'$.

Last edited: May 12, 2017