=====Electricity=====

====Circuits====
Power = watts, current (I) = amps, volts (E or V), resistance (R) = ohms
  * **Ohm's Law** e = ir
  * p = ie = 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: Vout = R₂/(R₁+R₂) * Vtotal, where R₂ is resistor between Vout and ground 

Joules = watts * seconds

====Capacitance====
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

**Coulomb's law**: Find force between two charged objects
  F = k * q₁ * q₂ / r²
    k = 9 * 10⁹ N m²/C²
    r = distance in meters
    C = coulombs
    C = Q/V = Q/Ed = A*epsilon/d

====Point Charges====

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