<img src="https://i.imgur.com/ZPadVTR.jpg"/>

E : the voltage corresponding to Ua - Ub = Uab
V = Ub - Uc
The current correponding to the flow of electrical electrons from A to C in A

**Dipoles :** component between two points of the diagram
**Ohm's law**: $V=R \times{I}$

<img src="https://i.imgur.com/a9skJL3.png" />

## Association of resistors
### resistors in serie
$R_{1}$ and $R_{4}$ get the same flow (current). Replace R1 and R4 by $R_{s} = R_{1}+R_{4}$
### Resistors in parallel
$R_{2}$ and $R_{3}$ see the same voltage:
$U_{2} = U_{c}-U{b}$, $U_{3} = U_{d}-U{b}$ and $U_{d} = U_{c}$
$R_{2}$ and $R_{3}$ are replaced by $R_{P}$ :
$R_{P}=\frac{R_{3}\times{R_{2}}}{{R_{3}+R_{2}}}$


## Definitions
- A branch is a link between 2 points in the diagram
- A node is a point in the diagram linked to at lease 3 branches
- A loop is a draw from a point in the diagram to itself. 
> ⚠️ In a loop we don't use the same path twice or more

Exemple: 
```mermaid
flowchart LR
	C --> D --> B --> C
```
```mermaid
flowchart LR
	A --> C --> B --> A
```

## Different laws
### Kirchhoff's laws
- The addition of voltages in a loop = 0 
exemple : $V_{AC} + V_{CB} + V_{BA} = 0$
- The algebraic sum of currents into a node = 0
Exemple : $\text{Node(C)} = I - I_{2} - I_{3} = 0$

### Kirchhoff's laws & Ohm's law 
We can't calculate $I$, $I_{2}$ and $I_{3}$
