Kirchhoff's Voltage & Current Laws — solve unknown drops and branch currents
The sum of all voltages around any closed loop = 0.
Vs = V₁ + V₂ + … + Vₙ
KVL: V_unknown = Vs − (V₁ + V₂ + … + Vₙ)
KCL: I_unknown = ΣI_in − ΣI_out_known
Based on conservation of energy (KVL) and conservation of charge (KCL).