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# System prepended metadata

title: Physics II - B3

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# Physics II - B3
## Electric Flux (Thông Lượng Điện)
* **Electric flux** is the **product** of the **magnitude of the electric field** and the surface area, A, **perpendicular to the field.**

> **Number of field lines ~ $E.dA.cos(\vec E, \vec n) = \vec E.d\vec A$**

### Open Surface
$$
\phi_E = \int_S \vec E. d\vec A
$$

$$
Units: [\frac{N.m^2}{C}]
$$

### Closed Surface
* **Net lines ~ $\displaystyle \phi_E = \oint \vec E.d\vec A$**
* **$\phi_E > 0 \to out > into$**

### Example
<img src = https://i.imgur.com/Oz8oL72.png width = 500 height = 300> <br>

**$\phi~total~ = 0 \to$ because electric field lines go in will go out.**



## Gauss's law
$$
\phi_E = \oint_S \vec E.d\vec A = \frac{q_{in}}{\epsilon_0}
$$

<img src = https://i.imgur.com/Sx6KkMg.png width = 350 height = 300><br>

**The electric flux of these non symetric surfaces = the electric flux of sphere.**

## Field Due to a Spherically Symmetric Charge Distribution
![](https://i.imgur.com/5H5Z0Fb.png)

## New words
* **hollow:** rỗng
* **solid:** đặc

## Other references
* [MIT Physics 2](https://www.youtube.com/playlist?list=PLyQSN7X0ro2314mKyUiOILaOC2hk6Pc3j)
* [Michel van Biezen](https://www.youtube.com/playlist?list=PLX2gX-ftPVXX7BZOcM1Y2gb8IQrTBrmUB)


 


