Equations Flashcards
Equation for current,time and charge
Q=IT, or i=dq/dt
Ohm’s Law equation
V=IR
Kirchoff’s Voltage Law (KVL)
In any closed loop of an electric circuit, the sum of the voltages across individual circuit elements in the loop is equal to zero
Kirchoff’s Current Law
Sum of current entering a node is equal to sum of current leaving the node
Resistors in series vs parallel
In series: Rt=R1+R2+…
In parallel: 1/Rt = 1/R1 + 1/R2 +…
Voltage Divider Equation
Vout=Vin * R2/(R1+R2)
For when resistors are in series
Where R2 is the resistor the voltage acts across
Current Dividor Equation
I2=Iin*R1/(R1+R2)
For when resistors are in parallel
For current through resistor 1( I1), use R2 on top
Equation for energy, charge and voltage
E=QV
Power equations involving power, voltage, resistance and current
P=VI
P=V^2/R
P=I^2R
Equation for frequency and period
f=1/T
Equation for angular frequency and frequency
ω=2πf
Equation for voltage,time, amplitude and angular frequency when dealing with a sinusoidal signal
V(t)=Asin(ωt)
Equation for current, voltage, resistance and angular frequency when dealing with a sinusoidal signal
i(t)=V/R sin(ωt)
Equation for charge, capacitance and voltage
Q=CV
Equation for current, voltage, capacitance and time (two forms for current and voltage)
i(t)=C*(dV(t)/dt)
V(t)=1/C * ∫i(t) dt
Equation for energy stored, capacitance and voltage
E=0.5CV^2
Capacitors in series vs parallel
OPPOSITE of resistors
Series: 1/CT = 1/C1 + 1/C2+…
Parallel: CT=C1+C2+…
What is transient analysis?
Equations for current and voltage across a capacitor thats charging-involves initial voltage, resistance, time and capacitance
Equation and definition of time constant
Analysis of a circuit over time once a capacitor begins to charge
i(t)=V0/R * e^(-t/RC)
V(t)=V0*(1-e^(-t/RC))
Time response of the circuit when a voltage is applied
Capacitor reactance definition and equation
Opposition to current flow in a capacitor
Xc=1/ωC
Diode definition, graph of voltage against current and most common use
Non-linear device that only allows current flow in one direction and dosn’t obey Ohm’s law
Looks like a x^3 graph that cross’s at (0,0)
Used as rectifiers in power supplies to convert AC to DC
FET definition
Field Effect Transitor. Voltage controlled device
Can turn on and off and also allow certain amounts of current through
How does a FET amplifier work?
Input voltage varies amount of current allowed through the FET (essentially changing its restance), this then diverts current from the output and so allows the output voltage to be amplified
Conductance definition and equation
Degree to which an object conducts electricity.
1/R=G, symbol is G
Equation for Thevenin equivalent circuit, Voc and Isc
Rthevenin = Vopencircuit/Ishortcircuit
Voc: voltage between A and B when there is no current flowing between A and B, open circuit
Issc: the current flowing between A and B when the circuit is closed, short circuit
