Certain reactions push electrons toward one terminal and pull them away from the other, making one side crowded and the other starved. This separation stores energy, like a stretched spring. The higher the battery's voltage, the stronger the separation.
Electrons inside the wire shift slightly, rearranging in response to the distorted space around the terminals. Then they stop, and everything settles.
The battery doesn’t release electrons into the circuit and walk away. It keeps working. Relentlessly. Preventing charges from neutralizing. Forcing the separation to exist.
That sustained separation reshapes space everywhere along the circuit at once. And as long as the battery keeps doing work, that reshaping does not relax.
This imbalance creates an electric field inside the wire — a field with a specific strength and direction, set by the battery's voltage. This field guides electrons to drift. But more importantly, this charge separation creates and maintains the entire electromagnetic field configuration around the circuit.
Without the battery continuously doing this work, the field would collapse, current would stop, and energy flow would cease.
Inside the wire, electrons drift slowly. When you flip the switch, the electric field snaps into place along the entire circuit, almost instantly. The electrons don’t race. They receive instructions.
The energy was never carried by electrons marching from battery to bulb.
But this field we are talking about isn't just electric.
Stationary charges create electric fields but when charges begin to move they also create another field, which we call the magnetic field. As Ampere stated, a current-carrying wire produces a magnetic field around it.
A magnetic field, born not from charge, but from motion.
Unlike electric fields, which push or pull, magnetic fields bend motion itself. They guide charges into curves without changing their speed.
So far we know moving charges are the cause, and a magnetic field is the effect.
Can a magnetic field, on its own, move charges?
After a decade of experimental pursuit, it turns out it can. In 1831, Faraday discovered that a changing magnetic field moves charges.
The story builds bit by bit. In 1861, James Clerk Maxwell took Faraday's experiments and field diagrams and translated them into mathematics. In those equations, he saw something more: if a changing magnetic field must create an electric field, then by mathematical necessity, a changing electric field must create a magnetic field.
Not because he observed it. Because the mathematics demanded symmetry.
You don't need moving charges. You don't even need a wire. A changing electric field alone, in empty space, could birth magnetism.
Maxwell worked through the consequences: if a changing electric field births a magnetic field, and that magnetic field births another electric field, the cycle doesn't stop. It needs no wires, no charges — only space. A self-sustaining field, propagating through emptiness at 3 × 10⁸ meters per second.
When you flip the switch, the field that snaps into existence is this self-sustaining wave, where electric and magnetic fields are locked in perpetual creation. We call it Electromagnetic.
But if these fields can sustain themselves and propagate through space, they must be carrying something with them. Not mass. Not charge. But energy itself.
When the bulb lights up, the energy isn't traveling through the copper wire; it's traveling through the electromagnetic field in the space around the wire. The electrons are just responding locally to that energy arriving from outside.