equations Flashcards
equation for force (F)
(k x Q1 x Q2 ) / d^2
k : Coulomb`s law constant, 9×109 N·m2/C2
d : distance between charges
Q1 : charge 1
Q2 : charge 2
equation for voltage (V)
W / Q
w : energy
Q : Charge
equation for current (I)
Q / t
Q: Charge
t = time
equation for resistance (R)
V / I
V : Voltage
I : Current
Equation for power (P)
I x V OR I^2 x R OR V^2/R
I : Current
V : Voltage
R : Resistance
equation for efficiency
Pout / Pin
Pout : Power output
Pin : Power Input
equation for conductance (G)
1 / R
R : resistance
equation for the sum of voltage drops in series circuit (kirchkoffs laws)
Vs = VR1 + VR2 + VR3…
Vs : total voltage drop
VRn : voltage across resistor n
equation for the voltage divider rule
RN / ( R1 + R2 + R3..) x Vs
Vs : source voltage
RN : single chosen resistor
R1/R2/R3 : each resistor
equation of total resistance in parallel circuit
1/R1 + 1/R2 … + 1/Rn
R1 = resistor 1
equation for current source
Is = Vs / Rs
equation for voltage source
Vs = Is x Rs
equation for output current in nortons theorem (IN)
Vs / RT
SO
IN = [R2 / (R2 + R3)] x Vs
equation for total resistance in nortons theorem
RT = R1 + (R2 x R3) / R2 + R3
equation for frequency (f)
1 / T
T : period
equation for period (T)
1/ f
f : Frequency
equation for capacitance ( C)
Q / V
Q : Charge
V : Voltage
equation for the energy stored in a capacitor (W)
1/2 x C x V^2
C : Capacitance
V : Voltage
equation for total capacitance when connected in series (CT)
1 / ( 1/C1 + 1/C2 + 1/C3…)
equation for voltage in RC circuits
vF + (vi - vF) x e ^-t/RC
vF : final voltage
vi : initial voltage
t : time
R : resistance
C : capacitance
equation for capacitor voltage when charging from zero (vi =0)
vF ( 1 - e ^-t/RC)
vF : final voltage
t : time
R : resistance
C : capacitance
equation for capacitor voltage when discharging from zero
(vF =0)
vi x e ^-t/RC
vi : initial voltage
t : time
R : resistance
C : capacitance
equation for instantaneous capacitor current (i)
C x dv/dt
c : capacitance
dv/dt : derivative of v with respect to time
equation for capacitive reactance (Xc)
1 / (2 x pie x f x C )
Pie : 3.14
f : frequency
C : capacitance
equation for reactive power (Pr)
Vrms x Irms
or
V^2rms / Xc
or
I^2rms x Xc
what is the polar form for voltage
(square root V^2R + V^2C ) < -tan-1 (Vc/Vr)
equations in ohms laws for RC circuits using Z,V & I
V = I x Z
I = V / Z
Z = V / I
equation of true power in RC circuits ( Ptrue)
I^2 x R
I : current
R : resistance
equation of reactive power ( Pr)
I^2 x Xc
Xc : capacitance reactive
I : current
equation for apparent power (Pa)
V x I
or
I^2 x Z
or
square root (p^2true + Pr^2)
V : voltage
I : current
Z : impendance
equation for impedance (Z)
square root [R^2 + (XL - XC)^2]
R : resistance
XL : inductive reactance
Xc : capacitive reactance
equation for instantaneous voltage across an inductor (V)
L x di/dt
L : inductance of coil
di/dt : time rate change of current
equation for the energy stored in a inductor (W)
1/2 x L x I^2
L : inductance of coil
I : current
equation for total inductors when connected in parallel (LT)
1 / ( 1/L1 + 1/L2 … 1/Ln)
Ln : each inductor
equation for time constant for inductors (t)
L / R
L : Induction
R : Resistance
general equation for current in RL circuits (i)
IF + (Ii - IF) x e^-Rt/L
IF : final current
Ii : initial current
R: resistance
t : time
L : inductance of coil
equation for an increasing current in RL circuits when Ii = 0
IF (1-e^-Rt/L)
IF : final current
R : resistance
t : time
L : Inductance of coil
equation for a decreasing current in RL circuits when IF = 0
Ii x e^-Rt/L
Ii : initial current
R : resistance
t : time
L : inductance of coil
equation of inductive reactance (XL)
2 x pie x f x L
f : frequency
L : inductance of coil
equation for true power in inductors
(Irms)^2 x Rw
Irms : instantaneous value of current
Rw : winding resistance
equation for reactive power in an inductor
Vrms x Irms
or
(Irms)^2 x XL
Vrms : instantaneous value of voltage
Irms : instantaneous value of current
XL : inductive reactance
equation for quality factor (Q)
XL/R
or
(2 x pie x f x L) / R when XL = 2nfL
XL : inductive reactance
R : resistance
f : frequency
L : inductance of coil
equation for resonant frequency (fr)
1 / [ 2 x pie x (squareroot L x C)]
L : inductance of a coil
C : capacitance
equation for cut off frequency in RC circuit
1 / ( 2 x pie x R x C )
R : resistance
C : capacitance
equation for cut off frequency in RL circuit
1 / ( 2 x pie x (L/R) )
L : inductance of coil
R : resistance
equation for output voltage in an RC circuit
[Xc / (squareroot R^2 + Xc^2) ] x Vin
Xc : capacitive reactance
R : resistance
Vin : input voltage
equation for output voltage in RL circuit
[ R / (square root R^2 + XL^2) ] x Vin
R : resistance
XL : inductive reactance
Vin : voltage input
equation for bandwidth
fr / Q
fr : frequency resonance
Q : quality factor
equation for upper cutoff point
fr + BW/2
fr : frequency resonance
BW : band width
equation for lower cutoff point
fr - BW/2
fr : frequency resonance
BW : band width
