# Introduction to electricity & electronics

## 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")