Join Robin Mitchell for an introduction to electronics, exploring what electricity is, how electric current flows, why voltage is always relative, and the differences between AC and DC power. By focusing on the fundamental principles before circuits and calculations, this episode builds the foundation needed to understand electronics from the ground up.
Follow along with Robin
Ask someone what electronics is and you'll often get an answer involving circuit boards, computers, sensors, robots, or perhaps a collection of mysterious symbols on a schematic. Yet before any circuit can blink an LED, process data, or control a motor, it all comes down to a handful of fundamental principles.
In this episode of element14 presents, Robin Mitchell begins a new educational series by stripping electronics back to its core concepts. Rather than opening with equations and circuit analysis, he focuses on building an intuitive understanding of electricity itself, examining what it is, why it moves, how engineers describe it, and the way voltage shapes every electronic system.
"Let's start from the absolute beginning. We're going to look at exactly what electricity is, how it works, and perhaps most importantly, why it works."
It is an approach aimed at helping newcomers understand the physical ideas behind electronics before moving on to components, circuit design, and practical projects.
Electricity is Simpler Than You Might Think
Despite powering virtually every aspect of modern life, electricity can be described in surprisingly simple terms.
"At its most basic level, electricity is simply the movement of electric charge from one point to another."
That movement of charge is what creates electric current. In the electronic circuits most makers and engineers work with, the charge carriers are electrons, tiny negatively charged particles that move through conductive materials.
Robin explains that electrons are not limited to travelling through copper wires. They can move through air during a lightning strike, through a vacuum as they did in CRT displays, and through conductive materials inside electronic equipment. Wires simply provide a convenient path that allows those charges to move where they are needed.
Using a plumbing analogy, he compares wires to pipes. Just as a pipe provides a route for water to flow from one location to another, a conductor gives electrons a route through a circuit.
The concept sounds straightforward, but it provides the foundation for everything that follows. Every power supply, sensor, processor, amplifier, and display ultimately relies upon electric charges moving in a controlled manner.
Electric Fields, Batteries, and Current Flow
Knowing that electricity is the movement of charge naturally leads to the next question: what makes charge move?
Robin introduces electric fields as the driving force behind current flow. Any electrically charged object creates an electric field around it. Those fields interact with other charges, causing attraction or repulsion.
"Like charges repel each other, opposite charges attract."
This behaviour is central to how electrical energy is stored and delivered.
A battery, for example, uses chemical reactions to separate charge between two terminals. One terminal develops an excess of electrons while the other develops a deficiency. As long as the battery remains disconnected, those charges simply remain separated. Once a conductive path connects the terminals, electrons have somewhere to go.
"They can travel out of the negative terminal along the wire and straight into the positive terminal. And that is an electric current flowing through a wire."
For beginners, this explanation often makes batteries easier to understand than thinking of them as mysterious sources of electrical energy. Rather than creating electrons, the battery creates the conditions that encourage charges to move when a complete path is available.
Robin also highlights a topic that frequently causes confusion when learning electronics: the difference between electron flow and conventional current flow.
Electrons physically travel from negative to positive. Engineers, however, normally analyse circuits using conventional current flow, where current is considered to move from positive to negative. The convention predates the discovery of electrons and remains the standard used in schematics, textbooks, and datasheets.
"Electrons move from negative to positive, but conventional current flow, the thing that all electronic engineers use, flows from positive to negative."
While it may appear contradictory at first, understanding both viewpoints helps when progressing to more advanced circuit analysis later in the series.
Voltage, Potential Difference, and Why Everything Is Relative
The largest portion of the episode is dedicated to voltage, a concept that often causes difficulties for newcomers because it is frequently introduced as a number before its meaning is properly explained.
Robin begins with a simple definition.
"Voltage is the difference in electrical potential between two points."
More specifically, voltage describes how much energy is available to a unit of charge moving between those points. A larger voltage means more energy can be transferred.
However, the principle Robin continually returns to is that voltage is never an absolute quantity.
"Voltage is relative. You cannot have a single point that is simply 10 volts. You have to say that it's 10 volts compared to something else."
To explain this idea, he compares voltage to measuring height. Saying something is ten metres high is incomplete unless a reference is provided. Is the measurement taken from the floor, a table, sea level, or some other location?
The same applies to electrical measurements. Voltage only exists as a comparison between two points.
This single concept unlocks many topics that can otherwise seem confusing. Components are not simply operating at a voltage. They operate at a voltage relative to a chosen reference point. Likewise, a voltage can appear positive or negative depending entirely on where the measurement starts and finishes.
Robin demonstrates this using a battery and a voltmeter. Swap the measurement probes and the reading changes from positive to negative, even though the battery itself remains unchanged.
The electrical potential difference still exists. Only the reference point has changed.
Understanding Ground
Once voltage is understood as a relative measurement, ground becomes much easier to explain.
In electronics, ground is often misunderstood as being the same thing as the Earth beneath our feet. Robin makes a clear distinction between the two.
Within a circuit, ground is usually the chosen reference point against which other voltages are measured. It represents the system's zero-volt baseline.
"In a circuit, we can choose almost any point to be our ground reference."
The important requirement is consistency. Once that reference has been selected, every other measurement is made relative to it.
In a battery-powered circuit, the negative terminal is commonly chosen as ground, but it does not have to be. A designer could just as easily choose the positive terminal as the reference point and describe the rest of the circuit relative to that location.
Robin also takes time to explain the relationship between ground, neutral, and earth within mains electrical systems, while reinforcing the importance of electrical safety. Understanding the terminology is useful, but working on mains-powered equipment should always be approached with appropriate training, procedures, and precautions.
AC and DC Explained
The episode concludes by introducing the difference between direct current (DC) and alternating current (AC).
Direct current maintains the same polarity over time. Batteries are a familiar example of a DC source, providing a voltage with a fixed direction.
Alternating current behaves differently. The polarity continuously reverses, causing the electric field and the movement of charge to repeatedly change direction.
"DC maintains the same polarity. AC, however, repeatedly alternates its polarity."
In the UK, mains electricity operates at 50Hz, meaning the waveform completes fifty cycles per second. During those cycles, the voltage repeatedly transitions between positive and negative values.
For someone beginning their electronics journey, this distinction is often sufficient. The detailed mathematics of waveforms, frequency, RMS voltage, and power conversion can come later. What is important at this stage is recognising that some sources provide a constant polarity while others continually alternate.
The Foundation for Everything That Follows
There are no resistors, capacitors, transistors, or microcontrollers in this first instalment. Instead, Robin focuses entirely on the principles that underpin every electronic circuit engineers build.
Electricity is the movement of charge. Electric fields are responsible for moving those charges. Batteries create a separation of charge that produces a potential difference. Current can be viewed either as electron flow or conventional current flow. Voltage is always relative, requiring a reference point, and ground provides a common reference for measurements throughout a circuit.
Those ideas may appear simple on the surface, but they form the basis of every schematic, PCB, and system an engineer encounters.
"Once you understand that, you have one of the most important foundations you'll ever need in electronics."
With those foundations in place, the series is ready to move on to the building blocks of practical circuit design, beginning with the three passive components that appear throughout electronics: resistors, capacitors, and inductors.
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