How Does Electricity Work?

Electricity is the movement of electrons through a conductive material — and in a typical household copper wire, those electrons drift at roughly 1 millimeter per second. The electrical signal itself, however, travels at close to the speed of light (about 2×10⁸ m/s in copper), which is why your light turns on the instant you flip the switch even though the electrons barely move.

The Atom Behind It All

Every atom has a nucleus of protons and neutrons, orbited by electrons. The electrons in the outer shells of some atoms — particularly metals like copper, silver, and gold — are loosely held and can be knocked loose relatively easily. These are called "free electrons" and they're the carriers of electrical current.

In a copper wire, there are roughly 8.5×10²⁸ free electrons per cubic meter — an almost incomprehensible density of charge carriers just sitting there waiting to be set in motion. The question is what sets them moving.

Voltage: The Push

Voltage is the difference in electrical potential between two points — essentially the "pressure" that drives electrons to move. A 9-volt battery has a potential difference of 9 volts between its terminals. Electrons at the negative terminal are at higher energy; they want to flow toward the lower-energy positive terminal, but they need a conductive path to do so.

Connect a wire (and a light bulb) between the two terminals and you've created that path. Electrons flow, current runs, and the bulb lights up. Remove the wire and break the circuit — current stops instantly. This is the on/off switch in every device you own.

Current: The Flow

Current is measured in amperes (amps) and tells you how many electrons are passing a point per second. One ampere equals approximately 6.24×10¹⁸ electrons flowing past per second. Your phone charger might draw 1-2 amps. A household circuit typically handles 15-20 amps. A lightning bolt can carry up to 20,000 amps — for about 30 microseconds.

The relationship between voltage, current, and resistance is captured by Ohm's Law: V = I × R (Voltage equals Current times Resistance). This three-variable equation governs every circuit ever built. Increase resistance with the same voltage and current drops. Increase voltage with the same resistance and current rises.

Resistance: The Friction

Not all materials let electrons move freely. Resistance is a material's opposition to electron flow, measured in ohms. Copper has very low resistance — ideal for wiring. Rubber has extremely high resistance — ideal for insulation. The resistance of a wire depends on its material, length, and thickness: longer and thinner means higher resistance.

When electrons flow through a resistive material, they collide with atoms and transfer energy — that energy becomes heat. This is how toasters and electric heaters work: high-resistance wire heats up when current flows through it. In LED bulbs, a different process converts electrical energy to light far more efficiently, which is why they run cooler than old incandescent bulbs.

AC vs DC — Why Your Wall Outlet Is Different From Your Battery

Batteries produce direct current (DC) — electrons flow in one direction continuously. Wall outlets produce alternating current (AC) — the direction of electron flow reverses 50 or 60 times per second (depending on your country). AC won the "War of Currents" in the 1880s against Edison's DC system because it can be stepped up to very high voltages for efficient long-distance transmission, then stepped back down at your home — a trick DC couldn't do easily at the time.

The electrons in your wall outlet never actually travel from the power plant to your home. They just oscillate back and forth locally. The energy travels as an electromagnetic wave along the wire.

Circuits — Putting It Together

A circuit is a closed loop that allows current to flow. Series circuits run all components in a single chain — if one breaks, all fail (old Christmas lights). Parallel circuits give each component its own path — one fails, others keep running (modern home wiring). The Circuit Builder game lets you construct your own circuits and see exactly how these configurations behave with visual current flow and voltage readings.

The same fundamental forces — electromagnetic fields, charged particles — also explain how certain materials stick together, which connects directly to the Element Fusion game, where atomic bonds drive the mechanics. For a more sandbox approach to physical interactions, Falling Sand simulates particle physics and material interactions in a way that shows how electrical properties like conductivity affect how matter behaves.

Electricity and magnetism are deeply linked — they're two faces of the same electromagnetic force. For more on the magnetic side, the post on how magnets work covers the field lines, poles, and surprising physics that make them function. And for how those electromagnetic principles power the technology connecting everyone, how WiFi actually works traces the signal from your router to your device.