V = R I
P = V I  =  R I^2  =  V^2/R

R    = ro() long. / S(sección)
       ro(cu) = 0.0172 ohms mm^2 / m

R(T) = R(20ºC) (1 + alfa() deltaT )
                    alfa(cu) = 4.3 10^-3 / ºK

Q    = 0.24 R I^2 t

V(t) = Vp sen ( w t )
                w = 2 pi f
Vm   = 0.637 Vp  =  0.9 Ve
Ve   = 0.707 Vp
Ve   = SQR{ (1/T) INTEGRAL[ 0...T ] ( V(t)^2 dt ) }

         XL = wL     XC = 1/wC        
Z  =   R  +  jwL   -   j( 1/wC )

P(trifásica) = SQR(3) Vfase Ifase cos( fi )

C = Q/V  = i t / V  --->  i = C dV/dt

Carga   : Vc = V ( 1 - e^( -t / RC ) )-->  t = -RC ln( 1 - Vc / V )
Descarga: Vc = V       e^( -t / RC )  -->  t = -RC ln(     Vc / V )

I = V t / L         --->  v = L di/dt
    V = cte.

i = I e^( -(R/L) t )

E(condensador) = -(1/2) C V^2
E(inductancia) = -(1/2) L I^2