Introduction to electricity & electronics

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Core electricity concepts

  • Charge, Voltage, Current
  • Resistance / Resistors
  • Capacitance / Capacitors
    • Common applications
      • storing energy (e.g. keeping your alarm clock set even when you unplug and change the batteries)
      • short bursts of powerful charge (e.g. camera flashes, tasers, nuclear detonators)
      • smoothing power (e.g. removing voltage spikes)
      • coupling / decoupling (i.e. letting AC pass or blocking AC, respectively)
      • sensors (e.g. capacitive touch screens)
  • Switches / Transistors
  • transduction
  • LEDs
    • typically drop ~2V (except blue and white, which drop ~4V)
    • typical max current = ~20mA


Important formulae

  • Ohm's law: V=IR
  • Voltage divider formula
  • Kirchhoff's laws:
    • Current Law: The amount of current entering a node in a circuit is equal to the amount of current exiting that node (i.e. "what goes in must come out")
    • Voltage Law: The sum of all voltage added and all voltage dropped in a closed loop circuit is zero. (i.e. "it all evens out in the end")


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