powering the system intro

Author: jeffchang0

docs/_sections/_guide-primaries/sensors-and-actuators/power.md

@@ -18,3 +18,17 @@ TODO write this
   - Is the single diode blocking DC input through the ESP32 good enough for power ORring? wouldnt that just damage the USB device
 
 - Include diagram of USBC breakout board
+
+# Intro to Power
+
+Electricity is an amazing property of physics that allows us to create infinite new technologies. Here you'll be learning about how it works, how to control it, and how it can destroy your components if you use it the wrong way!
+
+## Conductors, Voltage, and Current
+
+Conductors are materials that easily allow electricity to flow through them. You probably know a few, like metals and salt water. These materials 'conduct' electricity because electrons are shared between atoms in the material, creating a "sea of electrons". This "sea" allows electrons to bump into one another in the material, kind of like a Newton's Cradle.
+
+Voltage is the difference in electron density between two points in a conductor. If point A in a copper wire has less electrons and point B down the wire has lots, we say the "Voltage" between point A and point B is some number, say 3 Volts (the unit of measurement of voltage). 
+
+Let's keep imagining the copper wire, with points A and B. When there's a 3 Volt difference between points A and B, the electrons will want to rush from point B to point A to equalize the voltage in the wire, and this movement is called Current. Current is measured in Amperes (Amps), which is the number of electrons flowing perpendicular to a cross-section of a conductor. In the case of the copper wire, the current's positive direction is from point A to point B, even though the electrons are flowing the opposite way. This is because elctrons have a negative charge, and current is notated in the direction of positive charge flow (real fun, right?)
+
+One last concept in electric flow is Resistance, measured in Ohms. Resistance is the opposition to the flow of current, and it's how we control how much current we put into our components. Let's imagine our copper wire one last time. We have 3 Volts from point A to point B, and let's add a Resistor (a circuit component that adds resistance) between the two points. We can now find numeric values of Voltage, Current, and Resistance with the relationship V=I*R, where V=Voltage in Volts, I=Current in Amps, and R=Resistance in Ohms.