What happens?



How We Approach Electricity

  • Electricity can be beautifully described with physics and mathematics
  • However, we will focus on building an intuitive understanding and applying principles to build devices
    • There will be some basic math, but that is not our focus
  • Rules of Thumbs

Electricity Analogies

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Common Analogy

  • Electricity can be thought of as water flowing down a pipe

  • The higher the water falls from, the greater the pressure

  • More water can flow (and flow faster) through a larger and smoother pipe

  • If the water is stored in a container / vat, it will pour out until it is empty (like a battery)

Common Analogy

  • The “pressure” (or height) of the water is the voltage
    • Measured in units called volts (V)
    • Higher voltage means more potential energy
    • Our circuits will typically consider voltages 0v - 5v

Common Analogy

  • The “rate of flow” of the electricity is the current
    • Measured in units called amperes or amps (A)
    • Higher amperage means electrons are flowing faster
    • In equations, current with be denoted with the letter I
  • Note: 1 A is a lot! Our projects will consider smaller values such as 0.2 A.
    • Instead, we will say 0.2 A is 200 milliamps (mA)



Consider two equal water jugs connected to two different straws. Which has greater flow?



Resisting the Flow

  • The narrower pipes restrict or resist the flow of water
  • The measure of how well something resist or allows electricity is resistance
    • Measured in units called Ohms (Ω)
    • More Ohms means more resistance, which means less current (flow)

Key Concepts

  • Electrons are negatively-charged particles
  • Electricity is the flow of electrons from positive to **negative **(flow of energy)
  • Electronics is the study of devices that control / interact with the flow of electricity


  • Electricity will only flow if there is a circuit
  • A circuit is a complete loop from a positive voltage source to a negative (lesser) source, through a conductive material


Voltage as Difference

  • When we describe voltage, we are measuring the difference between two points
  • In the water analogy, water could fall from 500 ft to 400 ft, or from 100 ft to 0 ft
    • In both cases, water fell a difference of 100 ft, but the reference point changed
  • In a circuit, we commonly call the reference point Ground (GND) and say it is 0V

  • In homes and buildings, ground is literally connected to the earth

Voltage Source

  • In our circuits, we will use a voltage source to provide energy potential
    • USB power: 5v (also stepped down to 3.3v which the Argon uses)
    • 9V battery: 9v
    • Rechargeable lithium battery: 3.7v
  • Our circuits will have a positive voltage (e.g. 3.3v or 5v) and ground voltage (0v)
  • We will consider that current flows from the positive part of the circuit to the negative


  • Resistors conduct electricity, but are used to restrict / slow the flow of current
  • They can be connected either direction
  • We measure values from 0Ω to 10,000Ω
    • 10,000 Ohms is 10 kiloOhms (10 KΩ)

Accessibility Note

  • Resistor values are determined visually by color bands
  • Unfortunately resistor labeling is not accessibly designed
  • To support students who are color blind or have difficulty distinguishing colors, here are resources for support

Ohm’s Law

  • There are only a couple electrical laws that we need to know
  • There is a relationship between voltage (V), current (I), and resistance (R)
V = I * R
R = V / I
I = R / V
  • If you know two, you can solve for the other one



1.) The voltage source is 9v. If we have a resistor that is 300 Ohms, what is the current? 2) The voltage source is 9v and you want to provide a current of 9mA. What size resistor should we use?


  • We will use breadboards to connect our circuits
  • The power rails (on the long ends of the board) are all connected together
  • On the interior, each group of 5 pins are connected

Inside a Breadboard

  • Breadboards are built with rows and columns of connected pin sockets
  • Underneath each row and column are strips of metal that form electrical connections

Breadboard Connections

Breadboard Connections

Important Note

  • Different size breadboards are mostly identical, but note that the power rails are not connected the entire length of the board