# Homework Help: Calculating flux when charge on vertex of cube

1. Aug 24, 2010

### TsAmE

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

A point charge q = 112 x 10^-9 C is placed at the centre of a cube of side l = 0.2 m.

If the charge is moved all the way to one vertex of the cube, determine the flux
through each of the faces.

2. Relevant equations

None.

3. The attempt at a solution

Flux through each face = Total flux / 24
= 2 109.23 / 24
= 527 Nm^2/C

And dont understand why the 24 is used.

I read somewhere that it said that the flux through the faces adjacent to the vertex where the charge is placed = 0, but I dont understand why? I think this might be why I dont understand the use of the "24". Could someone please help?

2. Aug 24, 2010

### TsAmE

Sorry forgot to attach a diagram

#### Attached Files:

• ###### Cube.jpg
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3. Apr 28, 2012

### physicsblr

hi!
Flux through the faces touching the charge is zero because the Electric field is parallel to them. And flux through each face = ∅/24, since you have 24 faces in the cube diagram you attached.