The flow of electricity in AC circuits flips back and forth, unlike DC circuits

Tesla's alternating current power's most of the world's electric grids

In 1879, Thomas Edison’s light bulb relied on direct current, but such currents can't efficiently transmit power over long distances. Nikola Tesla introduced alternating current, which feature far fewer energy loses. Despite Edison’s attempts to discredit AC, Tesla proved its efficiency by lighting the 1893 Chicago World’s Fair.

Niagara Falls helped decide the battle between AC and DC power

In the 1890s, Niagara Falls became the proving ground for alternating current (AC) when Tesla and Westinghouse built the first large-scale AC hydroelectric plant—defeating Edison’s push for direct current (DC) in the US electrical system.

Alternating current was used to commit the first execution by electric chair

Dubbed the "executioner's current," the device was designed in Thomas Edison's lab by Harold Brown—an opponent of George Westinghouse and Nikola Tesla. The effort aimed at discrediting AC technology and gain favor for Thomas Edison's direct current as part of "The Current War."

How electrical transformers use coils of conductive wire to change voltage levels

Two sets of wires are wrapped around a magnetic core, each a different number of times. As alternating current flows through one wire, it generates a changing magnetic field that induces an alternating current in the second wire. If the second wire has fewer coils, the voltage steps down—decreases. If the second wire has more coils, the voltage steps up.

How electricity is generated by heating water into steam, which rotates magnets

Electrical current—the flow of electrons in a wire—can be produced when exposing a wire to a changing magnetic field. By rotating the magnets, as occurs in a turbine-generator system, the field changes become cyclical. This produces alternating current—flow that moves forward and backward—converting mechanical energy into electrical energy.

A dashboard showing real-time electricity usage in the US

The United States demands for electricity are enormous, with hundreds of thousands of megawatt hours required to run households and businesses every hour. You can track the fluctuations of US electric use with this dashboard.

Light energy can be transformed into electricity in solar cells via the photovoltaic effect

When light strikes semiconducting material, it can knock electrons out of atoms, creating a charge imbalance within the material. A wire connecting the oppositely charged regions can allow electrons to flow back, balancing the charges and producing an electric current that can be harnessed to power devices.

Fluorescent bulbs can be illuminated by overhead power lines without making contact

The electromagnetic fields produced by the alternating current in transmission lines can induce the motion of charges in nearby objects. This motion yields electric currents that can light up bulbs but are too small to harm humans.

The speed of electricity may refer to the movement of electrons or energy

In the 18th century, various experiments, including one in which monks holding an iron wire were shocked, suggested that electricity traveled at infinite speed. Advancements in technology, recognizing that electric currents were moving electrons, and the development of the theory of electromagnetism showed that electric signals can travel at near light speed, despite electrons moving much slower.

Lightning forms when streams of rising and falling charged particles connect

In cloud-to-ground lightning, a buildup of negative charge at the bottom of clouds repels electrons on Earth's surface, leaving behind positively charged particles. When descending negatively charged air—the stepped leader—meets rising positively charged particles—the upward streamer—brightening runs up the connection, producing intense flashes known as return strokes.

How its uneven rotation produces the sun's 11-year cycle and flips its magnetic poles

While charged material rises and falls in the sun's convection zone, which induces magnetic fields, different latitudes rotate at different rates, making these fields increasingly turbulent. This builds to a critical point—the solar maximum—where magnetic field-driven events, such as solar flares, become more common before the field collapses and flips, restarting the cycle.

Explaining how water's movement between different salt concentrations can generate electricity

Water naturally moves from regions of low salinity, such as freshwater, to regions of high salinity, such as ocean water, across a semipermeable membrane. This movement produces pressure that can be harnessed in osmotic power systems to drive turbines and generate electricity, much like in hydroelectric plants.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Boomerang earthquakes reverse direction and ripple back the way they came

Computer simulations show that rapid changes in friction along a fault where an earthquake has traveled for long distances can produce a smaller quake in the opposite direction. Data consistent with the phenomena has only been recorded a handful of times from 2011 to 2023.

How brain cells carry information

At any moment, there is an electrical storm coursing through your body. Discover how chemical reactions create an electric current that drives our responses to everything from hot pans to a mother’s caress.

Fluxgate magnetometers detect magnetic fields using electromagnets

Instead of a compass needle's movement indicating a magnetic field, an alternating current produces an oscillating magnetic field in a metal bar. An external magnetic field creates an imbalance in the oscillations, which can be measured quantitatively.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Transistors are the foundation of electronic signal processing

Small amounts of voltage can allow or block the flow of electrons across a transistor made from modified layers of semiconducting materials. The conducting (1) and insulating (0) states can be quickly modified as binary code is processed in a computer system.

The benefits and risks of smart grids, from improved efficiency to cybersecurity risks

By using a network of devices, including digital meters, sensors, and controllers, smart grids can quickly detect mechanical issues and fluctuations in supply and demand, automatically adjusting electricity flow to prevent cascading failures. While this is important for variable solar and wind power generation, many of these computer systems are designed to be controlled remotely, which increases the risk of malicious access.

Laminar flow moves in smooth, parallel layers, while turbulent flow is chaotic

In laminar flow, particles that make up a fluid move in consistent paths that do not cross each other. Contrastingly, differences across the speed of these particles cause them to mix, creating turbulence when viscosity cannot suppress the differences.

Faraday cages protect enclosed objects by redirecting electrical currents

Constructed from conductive materials, the cage allows electrons to distribute themselves evenly throughout its surface and travel to ground, keeping the interior neutrally charged and preventing any internal electricity. The same principle blocks electromagnetic waves by redirecting the electric field component, preventing telecommunication signals from entering the apparatus.

An overview of Earth's atmospheric cells and how they distribute Earth's uneven heating

The Hadley, Ferrel, and Polar cells are circulation patterns that act like gears, moving warmer air from the equator to the poles. The rising and falling of air currents within these patterns creates semi-persistent regions of low and high pressure, which contribute to the formation of regional climates, such as tropical zones.

Integrated circuits are made with light and require significant purified water and chemicals

The nonstop operation of fabrication plants, which takes months to manufacture a wafer of hundreds of integrated circuits, strains local resources and generates significant chemical waste. Much of the electricity consumed is used to maintain clean room conditions within plants.

The process of electronic funds transfer was approved in the US in 1978

An electronic funds transfer is the transfering of money from one bank account to another via computer-based systems. When it was first introduced, it was revolutionary. A video from 1980 aimed to explain the value of electronic funds transfer to consumers at the time.

Electric vehicle systems run on five key components

The system is made up of a charger—converting AC into DC—a battery, a power control unit, motor(s), and a single gear. A complex gearbox is not needed because electric motors are efficient at operating across a range of speeds.

How the Electoral College actually works

In settling on the rules for how the US elects presidents, the Founding Fathers coalesced around a system built on two inputs: Votes from individual voters, and the accumulation of votes from specially chosen Electors. The latter comprise the US Electoral College, and this Washington Post article explains why it exists, how it works, and how its 538 electors collectively decide presidential elections.

Most US House seats stay with the same party for decades

An analysis by the Pew Research Center shows that since the 1920s, the vast majority of House districts have been consistently won by the same party, with only a small share regularly changing hands. This highlights the large advantage incumbents have in House elections.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

How Amazon operates a 'flywheel' business model, a self-reinforcing cycle that drives continuous growth

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

Despite being favored by 87% of Americans, Congress does not have term limits.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

The American Society of Civil Engineers' infrastructure report card gave the US a C in 2025, its highest grade since the project launched in 1998.

A century of Billboard issues documenting the evolution of popular music.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Sony set the standard for cylinder-shaped batteries when it repurposed manufacturing equipment used to make rolls of magnetic recording tape.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

This site reaches millions of visitors who are tired of AI chatbots and seeking human connection. Pretend to be an AI chatbot and ask questions, provide answers, and draw for people in real time.

Scientists have struggled to pin down Ebola's natural reservoir species for decades, but the available evidence suggests that it's very likely fruit and insect-eating bats found in Africa.

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.