1. Electrical Theory Quantity Symbol Unit Equation
Charge Q coulomb Q = IIdt
Current I ampere I = dQ/dt
Voltage V volt V = dW/dQ
Energy W joule W = IVdt = IPdt
Power P watt P =dW/dt = IV
Resistor R ohm V = IR
Inductor L henry V = L dI/dt
Capacitor C farad V = 1/C IIdt

2. Electrical Theory Ohm’s Law I =V/R (DC) I = V/Z (AC) Kirchoff ’s Law
Sum of Loop Voltages = 0
Sum of Node Currents = 0
Joule’s Law
P = IE = I2R (I Squared R Loss)

3. Current Flow Electron Flow - From excess to deficient
Conventional Current Flow
Internal to Source (Battery)
Negative to Positive
External from Source (Battery)
Positive to Negative
Voltage Drop - Across a Resistor + to -
Negative Current - Assumed Direction Reversed

4. Equivalent Circuits Thevenin Two Terminal Resistor and Battery Circuit
Series Voltage Source and Equivalent Resistor
Voltage Source = Open Circuit Voltage
Equivalent Resistor = V / Short Circuit Current
Norton
Parallel Voltage Source and Equivalent Resistor
Current Source = Short Circuit Current

5. Series and Parallel Components
Component Series Parallel
R Req = R1 + R2 + R3 1/Req = 1/R1 + 1/R2 +1/R3
Z Zeq = Z1 +Z2 + Z3 1/Req = 1/Z1 + 1/Z2 + 1/Z3
l Leq = L1 + L2 + L3 1/Leq = 1/L1 + 1/L2 + 1/L3
C 1/Ceq = 1/C1 + 1/C2 + 1/C3 Ceq = C1 + C3 + C3

6. DC Circuit Components Component Impedance Current Power Energy
R R I = V/R None
L Zero Infinite WL = 1/2 LI2
C Infinite Zero WC = 1/2 CV2

7. AC Sinusoidal Analysis
Resistor R I = V/R P = I2R = V2/R
Inductor jXL= jwL I = -jVL/wL QL= I2XL = VL2/XL
Capacitor -jXC= -j/wC I = jVCwC QC= I2XC = VC2/XC
Current I = IR + j IX
Voltage V = VR + j VX
Complex Power S = VI* = (VR + j VX)(IR - j IX)
Complex Power S = P + j Q