# Homework Help: Curl div

1. Jun 14, 2010

### Engels

Curl div....

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

f is a scalar field. What does div(f) curl(f) rotgrad(f) divgrad(f) stand for?

I need to know if a scalar field can have the meanings of roration and diverge like a vector field

2. Jun 14, 2010

### lanedance

Re: Curl div....

if f is a scalar field, then grad(f) is a vector fields

div(f) makes no sense as f is a scalar, and div operates on vectors , curl(f) doesn't make sense for the same reasons

i'm guess rotgrad(f) = curl(grad(f)) which is ok, though i remember correctly its zero

have a look at this
http://en.wikipedia.org/wiki/Vector_calculus_identities

Last edited: Jun 14, 2010
3. Jun 14, 2010

### Dickfore

Re: Curl div....

div and curl are only defined for vector fields. grad is only defined for scalar fields.

The result of div is a scalar and the result of grad and curl is a vector. Therefore, these are the second spatial derivatives that you can construct:

$$\mathrm{div} (\mathbf{grad} \, \phi) = \nabla^{2} \, \phi$$

$$\mathrm{div} (\mathbf{curl} \, \mathbf{A}) = 0$$

$$\mathbf{grad} (\mathrm{div} \, \mathbf{A})$$

$$\mathbf{curl}(\mathbf{grad} \, \phi) = \mathbf{0}$$
$$\mathbf{curl} (\mathbf{curl} \, \mathbf{A}) = \mathbf{grad} (\mathrm{div} \, \mathbf{A}) - \nabla^{2} \, \mathbf{A}$$

where $\nabla^{2}$ stands for the Laplace differential operator (Laplacian).

4. Jun 14, 2010

### lanedance

Re: Curl div....

fixed up above - missed the curl(f) bit