Some selected Reference Equations for your use:
Voltage & Current dividers : (Resistors shown, but equally valid for impedances Z)
+
I
Ra
V
-
+
Rb
Ra
Rb
Vb = V.
Ra+Rb
-
Rb
Ib = I . Ra
Ra+Rb
I
CURRENT-DIVISION RULE
VOLTAGE-DIVISION RULE
A  jB (A  jB )( C - jD )

C  jD
C2  D2
General Thévenin Equivalent Circuit (TEC) : VT = Vab (OC) , i.e. the voltage across
terminals a-b with the load impedance removed. ZT = Zab („dead‟), i.e. the impedance
between the terminals a-b with the load impedance removed and with all source
values set to zero (= sources “killed”) . For Maximum power transfer: ZL = ZT* where
ZT* is the complex conjugate of ZT. When ZL = ZT* is satisfied, Pmax = (VT)2 / 4RT
where RT is the real part of ZT
Impedances:  (radians/sec)= 2f(Hz), ZR = R  0o , ZL = jL = L  +90o
ZC = 1/jC = - j /C = (1/C)  -90o.
Combinations of impedances follow the rules used for resistors.
Transformers: Voltage & Current transformations: Vp/Vs = Np/Ns = Is /Ip where Np &
Ns are the number of turns on the primary & secondary, respectively.
Impedance transformation : Zp = (Np/Ns)2 Zs
Power: DC Power calculations: PR = I V = I2 R = V2 / R
AC Power: Real or Average Power P = VI cos  (Watts), where VI is the „apparent
power‟(in volt-amps) and   is the phase angle between V & I
P= I2 Re Z where I = RMS current magnitude & Re Z is the real part of Z
Reactive Power Q = VI sin  (VARs), Q = P tan  and
Q= I2 Im Z where I = RMS current magnitude & Im Z is the imaginary part of Z
Complex Power S = P + jQ = VI* (Watts) , where I* is the complex conjugate of I.
Complex Number normalization :
3-Phase Power : Total Power in a balanced 3-phase Y or  load:
P= 3 VLIL cos  and Q = 3 VLIL sin where VL & IL are the line voltage and
line current and  is the phase angle between the phase voltage & phase current
For Y –loads: IL = Iph and VL = 3 Vph ; For  –loads: VL = Vph and IL = 3 Iph
For balanced loads, ZY = Z/ 3
Magnetic circuits: MMF = Ni ,
N= No. of turns, i = current (A).
Flux  = MMF/ Rm (Wb) , where Rm = Reluctance = l /A , (A-turn/Wb) , l = average
path length(m), A = area of cross-section(m2) and
Permeability  =r o , where r = relative permeability & o= „free space‟
permeability, o = 4(10)-7 H/m
Motors: Radians/sec to RPM conversion : (radians/sec) = (2/60)N(rpm) ,
DC Motors: Back-emf Eb = kam and Torque developed T = ka ia where ka is
the „armature constant‟,  is the „flux per pole‟, m is the speed (radians/sec), and ia (A)
is the armature current . For a given motor, the product (ka) can be assumed to remain
constant.
===============
1