Formulae, constants, laws, etc.
 Coulomb = C
 Electrons per coulomb: \( 6.241509745 * 10^{18} \)
 Coulombs per electron: \( 1.602 x 10^{19} \)
 Coulomb’s Law:
\[ \left  F \right  = k_{e}\frac{q_{1}q_{2}}{r^{2}} \] 
 … where
 \( k_{e} \) is a constant
 \( q_{1} \) is the charge of the first particle in Coulombs
 \( q_{2} \) is the charge of the second particle in Coulombs
 r is the distance between them in meters
 F is the force in newtons
 m is meters
 N is Newtons
 \( k_{e}=8.988 \ast 10^{9} \frac{Nm^2}{C^2} \)
 Meter: Abbreviated m.
 Centimeter: Abbreviated cm.
 Newton: Unit of force. Force needed to accelerate 1 kilogram of mass at the rate of 1 meter per second squared. Abbreviated N.
 Amp: Unit of current. Abbreviated A.
 Amps = Coulombs / seconds
 \( A=\frac{C}{s}\)
 Joule: Unit of work (or energy expended). Abbreviated J. Newtons * meters.
 1 Joule = passing an electric current of one amp through a resistance of one ohm for one second
 Other measures of work/energy expended:
 Watts * seconds
 Coulombs * volts
 Volts are joules divided by coulombs. i.e. 1V = \( \frac{1J}{1C} \)
 Watts:
 Joules per second
 Volts * Amps
 Current arrows
Forward (positive):
From plus, through to minus is forward (consuming power).
Reverse (negative):
From minus, through to plus is backward (generating power).
For voltages, + connected to + is forward.
Another way of diagramming the same thing
 Ohm’s Law:
 v = iR
 If current arrow is from minus, through to plus, then use v = iR
 \( \Omega=\frac{V}{A} \)
 Volts / Amps
 v = iR
 Metric prefixes
 k = kilo = \( 10^{3} \)
 M = mega = \( 10^{6} \)
 c = centi = \( 10^{2} \)
 m = milli = \( 10^{3} \)
 \( \mu \) = micro = \( 10^{6} \)
 Kirchhoff’s Current Law: The sum of all currents entering a node = the sum of all currents leaving a node.
 Resistors in series: \( R_{1} + R_{2} + R_{3} \)

Resistors in parallel: \( \left ( \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}} \right )^{1} \) or use \( \frac{R_1 R_2}{R_1 + R_2} \)

Voltage divider (using resistors in series): \( v_1=\frac{R_1}{R_1+R_2}v \)

Current divider (using resistors in parallel): \( i_1=\frac{R_2}{R_1+R_2}i \)
 Capacitance in Farads:
\[ C = \frac{Q}{V} \]
 C = Farads
 Q = Coulombs
 V = Volts
 1 microfarad = 1 \( \mu \)F \( = 1 \times 10^{6} \) farad
 1 picofarad = 1 pF = \( 1 \times 10^{12} \) farad = 1 micro microfarad