Equations

Question 1

Equation for current,time and charge

Answer 1

Q=IT, or i=dq/dt

Question 2

Ohm’s Law equation

Answer 2

V=IR

Question 3

Kirchoff’s Voltage Law (KVL)

Answer 3

In any closed loop of an electric circuit, the sum of the voltages across individual circuit elements in the loop is equal to zero

Question 4

Kirchoff’s Current Law

Answer 4

Sum of current entering a node is equal to sum of current leaving the node

Question 5

Resistors in series vs parallel

Answer 5

In series: Rt=R1+R2+…

In parallel: 1/Rt = 1/R1 + 1/R2 +…

Question 6

Voltage Divider Equation

Answer 6

Vout=Vin * R2/(R1+R2)
For when resistors are in series
Where R2 is the resistor the voltage acts across

Question 7

Current Dividor Equation

Answer 7

I2=Iin*R1/(R1+R2)
For when resistors are in parallel
For current through resistor 1( I1), use R2 on top

Question 8

Equation for energy, charge and voltage

Answer 8

E=QV

Question 9

Power equations involving power, voltage, resistance and current

Answer 9

P=VI
P=V^2/R
P=I^2R

Question 10

Equation for frequency and period

Answer 10

f=1/T

Question 11

Equation for angular frequency and frequency

Answer 11

ω=2πf

Question 12

Equation for voltage,time, amplitude and angular frequency when dealing with a sinusoidal signal

Answer 12

V(t)=Asin(ωt)

Question 13

Equation for current, voltage, resistance and angular frequency when dealing with a sinusoidal signal

Answer 13

i(t)=V/R sin(ωt)

Question 14

Equation for charge, capacitance and voltage

Answer 14

Q=CV

Question 15

Equation for current, voltage, capacitance and time (two forms for current and voltage)

Answer 15

i(t)=C*(dV(t)/dt)

V(t)=1/C * ∫i(t) dt

Question 16

Equation for energy stored, capacitance and voltage

Answer 16

E=0.5CV^2

Question 17

Capacitors in series vs parallel

Answer 17

OPPOSITE of resistors
Series: 1/CT = 1/C1 + 1/C2+…
Parallel: CT=C1+C2+…

Question 18

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

Answer 18

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

Question 19

Capacitor reactance definition and equation

Answer 19

Opposition to current flow in a capacitor

Xc=1/ωC

Question 20

Diode definition, graph of voltage against current and most common use

Answer 20

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

Question 21

FET definition

Answer 21

Field Effect Transitor. Voltage controlled device

Can turn on and off and also allow certain amounts of current through

Question 22

How does a FET amplifier work?

Answer 22

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

Question 23

Conductance definition and equation

Answer 23

Degree to which an object conducts electricity.

1/R=G, symbol is G

Question 24

Equation for Thevenin equivalent circuit, Voc and Isc

Answer 24

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