.png)
How Electricity Really Works in a Circuit: A Clearer Picture
When you flip a light switch, the bulb lights up instantly.
You might think electrons flow through the wires, carrying energy from the battery to the bulb.
That’s a common idea, but it’s not quite right.
The Old Idea: Electrons Moving Inside Wires
Traditionally, electricity is like water in pipes: the battery pushes electrons inside wires to the bulb (the "load") and back.
But electrons move slowly—about 73.4 μm/s.
For a 1-meter distance, they’d take minutes to arrive, yet the bulb lights up in 6.67 ns.
Something else is at play.
The Real Story: Electromagnetic Fields Carry the Energy
Electricity is the flow of electromagnetic (EM) fields channeled in the space between the wires:
- Closing the switch sets up an electric field.
- This field, with a magnetic field, forms an EM wave that travels between the signal conductor and return and reference conductor, like water between riverbanks.
- The wires guide the EM fields, preventing leaks that could cause electromagnetic interference (EMI).
- The EM wave delivers energy to the load at 150 million m/s in a typical PCB.
- Electrons move slowly (73.4 μm/s) in response to the induced field, not as the cause.
In the circuit:
- Source (battery) generates the EM field.
- Signal and Return Conductors channel the EM wave to the load.
- Load (bulb) converts the energy into light or heat.
Why the Old Model Fails
- The "electrons flowing" idea suggests they carry energy, but they’re too slow.
- The EM wave, delivers energy much faster.
A Simple Analogy
- The wires are riverbanks, and the energy is water flowing between them at 150 million m/s.
- The riverbanks guide the water, preventing leakage and EMI.
Why This Matters
This explains instant light activation, efficient power lines, fast computers, and better circuit design to minimize EMI.
Next time you are designing your electronic circuits, remember: it’s the EM wave between the conductors delivering energy — not the electrons!
-Dario
PS. If you want to learn PCB design and EMC/EMI Design the intuitive way, grab one of my courses or EMI control guides here: