The Ungerecht Family Tree

Power = watts, current (I) = amps, volts (E or V)

• Ohm's Law e = ir
• p = ie
• p = i²r

Resistors in series add together
Resistors in parallel: 1/Rt = 1/R₁ + 1/R₂ + ...

current in parallel: if have V, compute R for each path 
For two paths, R₁ & R₂: I on R₁ = R₁/(R₁+R₂)

Voltage divider: (R₂ is resistor between Vout and ground)
Vout = R₂/(R₁+R₂) * Vtotal 

Q = CV , Q = charge (coulombs, always a positive value),

       C = capacitance (farads), V = voltage

parallel plate capacitor C = epsilon (A/d), A = area, d = distance between plates

epsilon = permittivity of the dielectric
dielectric constant (over free space) = 8.84 * 10⁻¹² Farads/meter

Electric field E = V/d (volts/meter)

E = sigma/epsilon,  sigma = charge density
sigma = Q/A

Force between two charged objects: Use coulomb's law:

F = k * q1 * q2 / r²
  k = 9 * 10⁹ N m²/C²
  r = distance in meters
  C = coulombs