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Electronics Formulas

of Electronics Component

BASIC ELECTRIC CIRCUITS
OHM'S LAW


 

KIRCHOFF'S LAWS

    The sum of the voltage drops around a series circuit equals the applied voltage

    E(applied)=E1+E2+....En

    The current flowing toward a point in a circuit must equal the current flowing away from that point

    I(in)=I(out)1+I(out)2+...I(out)n

Unknown
Value
Formula
E
I
P
R
    E = voltage in volts
    I = the current in amperes
    P = the power expressed in watts
    R = the risistance in ohms
Resistance Circuit
Series Connected

R(tot) = R1 + R2 + . . . Rn

Paralel Connected

2 Paralel Connected Resistor

Capacitance Circuit
Paralel Plates


    A = in square centimeter
    d = in centimeter
    K = dielectrict constant between the plates

Charge Stored

Q = CE

    Q = the charge in coulumbs
    C = the capacitance in farads
    E = the voltage impressed across the capacitor

Energy Stored

    W = the energy in joules (watt-seconds)
    C = the capacitance in farads
    E = the applied voltage in volts
Paralel Connected

C(tot) = C1 + C2 + ....Cn

Series Connected

 

2 Series Connected

    The voltage across each capacitor connected in series is proportional to the total capacitance divided by the capacitance of the capacitor

RC Time Constant
   
    E(t) = Capacitor EMF in volts at t
    E(s) = potential of charging batteries in volts
    t = time in seconds
    e = natural logarithmic base = 2.718
    R = resistance in ohm
    C = Capacitance in farads
T = RC
    Theoritically charging time is never finished, for mathimatical reasons the above formula is taken, based on the capacitor voltage increases/decreases up to/by 63 % of the applied/initial voltage
    T = time constant in seconds
    C = capacitance in farads
    R = resistance in ohm
Inductance Circuit
Series connected

L(tot) = L1 + L2 + . . .Ln

Paralel Connected

2 Paralel Connected Inductors

Mutual Inductance of 2 coils:

    M = mutual inductance expressed in
    the same unit as La and Lb
    La is the total inductance of l1 and l2
    with fields aiding
    Lb = the total inductance of L1 and L1
    with field opposing
Coupling coeficient:

    K = coupling coeficient
    M = mutual inductance
    L1 L2 inductance
Reactance
Capacitive


    Xc= Reactance in Ohms
    f = frequency in Hertz
    C= in Farad
Inductive

    Xl = Reactance in Ohms
    f = frequency in Hertz
    L = in Henry
RESONANCE


F = Resonant frequency in Hertz
L = inductance in Henry
C = Capacitance in Farad


 


Updated April, 1998