Digital Electronics & Computer Architecture

Courses

In Progress

Author

Tyler Hillery

Published

May 10, 2026

Notes

The Ancient Greek work for amber is elektron. Thales of Miletus observed around 600 BC that rubbing amber attracted light objects.
In 1600, English Philosopher William Gilbert was first to coin the term electricitus, behaving like amber, as he recognized this behavior in other materials.
In 1746, the Leyden Jar was used to store high-voltage electric charge. In modern terms this is called a capacitor.

In 1897, Joseph John Thomson discovered the electron by showing that cathode rays in a vacuum tube were made of tiny, negatively charged particles much smaller than atoms.
Voltage is the electric potential difference between two points in a circuit.
Electrons flow from negative charge (more electrons than protons) to positive charge (more protons than electrons). This flow is called current, flow of electrons from one point to another. We measure current in amps.
“Holes” move in the opposite direction, positive to negative. This is also called the Electric Field, also called Conventional Current.
The positive end is also called the “attractor” while the negative end is called the “source”.
The resistance makes it difficult for electrons to move, limiting the amount of current that can flow. Measured in ohms.
Ohm’s Law: \(I = \frac{V}{R}\)
- \(I\) = current (amperes)
- \(V\) = voltage (volts)
- \(R\) = resistance (ohms)

Watt (W) measures the rate at which energy is produced, transferred or consumed. Energy is measure in Joules (J) so \(Watt = J/s\)
Voltage measures how much energy per unit of charge is available to move electric charges.
1 volt is the pressure that represents of work/energy (Joules) needed to move a certain amount of charge Coulombs \(1V = 1\frac{J}{C}\)
My mental model of Coulombs is like X amount of electrons
We can also state the 1 volt as the potential difference across two points of a conductor when a current of 1 ampere(A) dissipates 1 watt (W) of power between those points \(1V = 1\frac{J}{A}\)

When electric current runs through a conductor it creates a magnetic field around the wire
A changing in magnetic field can induce an electric in a conductor (electromagnetic induction).
Coil shapes have more inductance than a straight shape. More turns of wire means that the coil will generate a greater amount of magnetic field force for a give amount of coil current.
This magnetic field can be used to have a small amount of current to create a magnetic field that will attract this arm that can create a connection in another circuit which can be high power. This idea is the basis for relays.
It’s important to understand this above “relay” has two different circuits, which are isolated from each other. The lower power part is sometimes called a “small control signal”. This also applies to vacuum tubes and transistors.
DC has a lot of resistance through the wire and loses a lot through the transmission mainly through heat.
AC (alternate) uses transformers to increase the voltage, because we want high voltage low current for transmissions. Then we step down when arriving to homes to make voltage smaller so it’s safer.
There is HVDC (high voltage DC) now which is more efficient than AC.
Inductors store energy in the magnetic field when current flows through it. Whereas capacitors store energy in the electric field