- #1

- 124

- 0

- Thread starter Pupil
- Start date

- #1

- 124

- 0

- #2

- 124

- 0

No one knows?

- #3

Doc Al

Mentor

- 45,029

- 1,329

The ε

Last edited by a moderator:

- #4

- 4,662

- 5

C = e

where the permittivity of free space e

and the permeability of free space is

u

- #5

jtbell

Mentor

- 15,733

- 3,889

Using [itex]\epsilon_0[/itex] Coulomb's Law is more complicated:

[tex]F_{elec} = \frac {1} {4 \pi \epsilon_0} \frac {q_1 q_2} {r^2}[/tex]

but other equations like Gauss's Law and the parallel-plate capacitor equation are simple:

[tex]\vec \nabla \cdot \vec E = \frac {\rho} {\epsilon_0}[/tex]

[tex]C = \frac {\epsilon_0 A}{d}[/tex]

Whereas using k, Coulomb's Law is simpler:

[tex]F_{elec} = k \frac {q_1 q_2} {r^2}[/tex]

but you have to insert factors of [itex]4 \pi[/itex] into other equations:

[tex]\vec \nabla \cdot \vec E = 4 \pi k \rho[/tex]

[tex]C = \frac {A}{4 \pi k d}[/tex]

- #6

madmike159

Gold Member

- 369

- 0

Well 1/4pi*e0 is where 9x10^9 came from.

- Last Post

- Replies
- 6

- Views
- 2K

- Replies
- 4

- Views
- 2K

- Last Post

- Replies
- 13

- Views
- 5K

- Last Post

- Replies
- 4

- Views
- 1K

- Last Post

- Replies
- 10

- Views
- 6K

- Last Post

- Replies
- 7

- Views
- 4K

- Last Post

- Replies
- 11

- Views
- 20K

- Replies
- 1

- Views
- 671

- Replies
- 12

- Views
- 14K

- Replies
- 3

- Views
- 2K