What if electricity traveled without wires?

Lamps, fridges and chargers all plug into the wall.

Wires carry the electricity. What if electricity could fly through the air instead?

Look around a room and you'll see wires everywhere: lamp cords, phone chargers, and cables hidden in the walls. Outside, power lines on poles and towers carry electricity from power plants to homes.

But some phones already charge just by lying on a pad, with no plug at all. So here is a thought experiment: what if all electricity could travel without wires? You can explore how charging pads work, whether radio waves can carry power, and why wires are still hard to beat.

Electricity reaches us through a grid of conductors: transmission lines, distribution lines and building wiring. Wireless power transfer already exists at small scale, in charging pads, contactless cards and tags, and in experiments that beam energy as microwaves or light.

This thought experiment asks how far wireless transfer could go. The key physics is coupling: how much of the energy leaving a transmitter actually reaches the receiver. That depends strongly on distance, alignment and the way the energy travels, through a shared magnetic field or as a radiated wave.

Big wires carry electricity from power plants to our homes.

A tiny bit of electricity gets lost on the way. But most of it arrives.

Our electricity travels through a huge web of wires called the grid. Long-distance lines carry it from power plants to towns, and smaller lines carry it along streets and into buildings.

Wires do this job very well. The U.S. Energy Information Administration estimates that about 5 percent of the electricity sent through U.S. transmission and distribution lines was lost on the way each year from 2018 through 2022. In other words, about 95 percent arrived where it was needed.

The grid steps voltage up with transformers for long-distance transmission, then down in substations for distribution; OpenStax notes that local distribution runs at about 5 to 13 kV before a final step down to 120, 240 or 480 V at the user's site.

The U.S. Energy Information Administration estimates that transmission and distribution losses averaged about 5 percent of the electricity transmitted and distributed in the United States in 2018 through 2022. That is the benchmark any wireless alternative would need to approach.

Let's pretend there are no plugs or cords at all.

Your phone charges on the table. A car charges while it is parked. But could a whole town work this way?

Imagine phones charging on any tabletop, buses charging at every stop, and no cords to trip over. Some of that already works over short gaps. Oak Ridge National Laboratory charged a car without wires through a gap of 4.75 inches, about 12 centimeters.

But sending power across a room, a city or from space is much harder. Energy sent out into the air spreads out as it travels, so less reaches the target. These are big engineering puzzles, and scientists are still exploring which ones could be solved.

Short-gap inductive links behave much like a transformer whose core has been removed: efficiency is high when the coils are close and aligned. Oak Ridge National Laboratory reported more than 95 percent efficiency at 270 kW across a 4.75-inch gap.

At longer range, energy must be radiated. A radiated signal spreads over an area that grows with the square of the distance, so the receiver captures a shrinking share unless the beam is tightly focused. Researchers have beamed small amounts of power from orbit, and NASA has studied space-based solar power, but how far wireless delivery could scale is an open question.

A charging pad has a coil of wire inside. So does the phone.

Electricity in the pad makes a changing magnet field. The field makes electricity in the phone!

A wireless charger works by electromagnetic induction. Inside the pad is a coil of wire. When an alternating current flows through it, it makes a magnetic field that keeps changing. A second coil inside the phone or car sits in that field, and the changing field pushes electric current around it.

This is the same idea that makes a transformer work. In a transformer, both coils are wound around an iron core that guides the magnetic field. A charging pad has an air gap instead, so the coils must be close and lined up.

Faraday's law: a changing magnetic flux through a coil induces an emf proportional to its rate of change. A transformer couples its primary and secondary coils through an iron core that traps the field, and only changing currents induce a voltage, which is why transformers do not work with steady DC (OpenStax §23.7).

An inductive charger removes the core and relies on the coils' shared field across an air gap. As the gap grows or the coils slip out of line, less of the primary's flux links the secondary. ORNL's design boosts power density with polyphase coils that create a rotating magnetic field.

Some tags in shops and libraries have no battery. A reader sends out radio waves that power them.

Scientists even sent a little energy from space to the ground!

Wireless power is already around you. The U.S. Food and Drug Administration explains that passive RFID tags, used to track things, have no battery: they are powered by the reader's radio waves.

In 2023, a Caltech experiment in orbit used microwaves to light up small LEDs about a foot away and sent detectable power to a receiver on a roof in Pasadena, California. And a 2024 NASA study found that a space solar power system starting in 2050 would cost more than ground-based alternatives, though costs could fall if technology gaps are solved.

FDA: passive RFID tags are powered by the reader and carry no battery. Caltech's MAPLE, launched January 3, 2023, used a flexible microwave array to power receivers about a foot away, and on May 22 its beamed energy was detected on a rooftop at Caltech in Pasadena.

NASA's Office of Technology, Policy, and Strategy (January 2024) found that a space-based solar power system beginning operation in 2050 would be more expensive than terrestrial sustainable alternatives, noting gaps in in-orbit assembly, autonomy and efficient power beaming, and that costs could fall if those are addressed.