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**: $V=R \times{I}$ ## 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 $I_{3}$