diff --git a/Electronic/Lecture 1.md b/Electronic/Lecture 1.md
index 2676728..7b02475 100644
--- a/Electronic/Lecture 1.md	
+++ b/Electronic/Lecture 1.md	
@@ -4,3 +4,35 @@ 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" /i>
+
+## 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. 
+	Exemple: 
+```mermaid
+flowchart LR
+	C --> D --> B --> C
+```
+```mermaid
+flowchart LR
+	A --> C --> B --> A
+```
+
+## Diferents 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 : $\text{Node(C)} = I - I_{2} - I_{3} = 0$