**Kirchhoff's**

series: I const, V divider

parallel : I divider, V const

**Ohm's**

V = IR

I = V/R

R = V/I

**Power**

P = IV

**Reactance / Inductance**

Xc = 1/(2πfC)

Xl = 2πfL

Z = sqrt(R\*\*2 + X\*\*2)