# What does the black point mean when we are calculate the inductance of several inductors which connected together?

What does this black point mean?i mean because what reason ,so we will say the inductance of the circuit below can be written as this,by the way , $$\M\$$ means Mutual inductance. Also,i want to ask that Why can the inductance of the circuit below be calculated like this? $$\L_{AB}=L_1+L_2+L_3+2M_{12}-2M_{13}-2M_{23}=3+7+10+(2\times2)-(2\times1)-(2\times 3)=16H\$$

• The black point means, the "polarity" of the coils in relation to each other. – vtolentino Apr 30 '20 at 13:26
• do you understand what mutual inductance means? The dots simply represent the polarity of the influence the inductors have on each other – FrancoVS Apr 30 '20 at 14:05
• @shineele do you understand what mutual inductance is about? – Andy aka Apr 30 '20 at 14:30
• @Andyaka Not totally understand about mutual inductance – shineele Apr 30 '20 at 14:56
• OK, wasn't sure from the way you phrased the question. – Andy aka Apr 30 '20 at 14:58