While charges consistently move in the same direction in a direct current, the flow of charges changes multiple times per second in an alternating current.

Visualize how alternating currents—electricity that periodically changes direction—are generated by rotating magnetic fields, as occurs in turbine-generator systems.

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.

The speed of electricity may refer to the movement of electrons, which is on the order of a fraction of a millimeter per second, or energy, which is near the speed of light.

Transformers change the current and voltage across a set of wires by wrapping them around a magnetic core and using the magnetic field of one wire to induce a current in the other.

Watch a timeline of the history of electricity, from observations of static electricity in antiquity to the War of the Currents between Nikola Tesla and Thomas Edison to establish the ideal system for electric grids.

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."

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.

View the various types of lightning

The most common form of lightning involves channels of electricity between oppositely charged regions within a cloud or between two clouds to reestablish electrostatic equilibrium. While cloud-to-ground lightning is understood best, research is ongoing to fully model the mechanisms behind rarer forms of lightning, such as transient luminous events.

Electricity can be lethal because it can disrupt the nervous system, which controls critical bodily functions such as breathing and heart rate, which rely on electrical signals between cells.

The engineering underlying the electric grid and why it needs to be modernized

The system includes generators for producing electricity and millions of miles of transmission and distribution lines to transport the energy. The substantial increase in the number of electronic devices and electrical demand since the construction of much of the grid in the mid-1900s has strained infrastructure, requiring continuous upgrades and massive investments in new construction.

Watch lightning strike a building at 40,000 frames per second

When the built-up layer of negative charge at the bottom of clouds is sufficiently high, a network of charge filaments will emerge. If one of the filaments meets a rising strand of positively charged particles, a highly conductive path forms, and charges across all filaments move to the path, generating lightning

On average, every in-service airplane is struck by lightning once a year

The average strikes per surface area per year on Earth suggest that aircraft should only be struck once every 1,000 years, based on their size, but proximity to storm clouds' high electrical fields increases strike rates. Aircraft are designed as continuous conductive shells, causing electricity to flow along their exterior and preventing internal damage.

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.

George Westinghouse purchased Tesla's AC technology patents for $60,000

The seven patents in alternating current motors and power transmission formed the basis for a system of technologies including generators, transformers, and lighting. Nikola Tesla spent half the funds on a new laboratory to develop new inventions.

As of 2025, China used the most electricity of any country, accounting for 33% of the total global demand and more than twice that of the US.

While gas-powered engines typically have 2,000 moving parts, electric vehicles have about 20.

Lightning rods provide a conductive pathway to safely steer massive electric currents

The device is positioned higher above the ground to "catch" one of the many branching filaments of electrons from clouds before they make contact with other surface structures, which have been induced to have a positive charge by overhead storm clouds. The current is then sent to a conductive grid buried underground.

Despite electric usage concerns, EV charging accounts for less than 1% of grid load

Other popular myths about EVs include battery failure concerns—failure rates are less than 1% on newer models—and that there are no places to charge cars, though both at-home outlets and more than 77,000 stations on the road are available.

Electricity is produced when the ends of a battery are connected by a conducting wire, triggering chemical reactions that release the energy stored in chemical bonds.

Electricity can flow indefinitely along a ring of superconducting material, which provides zero resistance to the movement of charges due to quantum effects.

Thomas Edison publicly executed animals with AC to convince the public of its dangers

J.P. Morgan first backed Thomas Edison's direct current system, seeing electricity's potential to usurp John D. Rockefeller's kerosene empire. Despite the investments and smear campaign against alternating current, alternating current ultimately won public support after lighting the 1893 World's Fair, after which Morgan would fund Tesla's wireless transmission tower.

Electromagnetic induction creates electricity from a changing magnetic field

The phenomenon was discovered in 1831 by Michael Faraday when an electric current was induced in a wire wrapped around an iron ring after a second wrapped wire not connected to the first was connected or disconnected from a battery.

The air around lightning can be five times hotter than the sun's surface

The rapid discharge of electricity—flowing electrons—between oppositely charged regions across a narrow filament can raise temperatures to 30,000 degrees Celsius (54,000 degrees Fahrenheit). If lightning strikes a tree, the speed of the temperature spike can almost immediately turn all its water into pressurized steam, causing it to explode.

On average, the human body produces about 100 watts of electricity—enough to power a light bulb—but some people can produce over 2,000 watts in short bursts, such as when sprinting.

The unpredictability and brevity of lightning make lightning power impractical

While a typical lightning strike provides 30,000 amps at 300 million volts, the bolt only lasts about 30 microseconds. If the electrical surge could be captured—assuming one knew beforehand where it would strike—it would only provide enough electricity to power one home for about 6.4 hours.

The characteristic zigzag of lightning originates from columns of conductive oxygen

Energized electrons from the base of clouds collide with oxygen molecules, placing them in a "singlet delta state," which makes the air conductive. Collisions continue until more than 1% of nearby oxygen is in this state—about 0.00005 seconds—matching the electrical potential of the cloud and propogating electricity in a 50-meter "step."

In the photovoltaic effect, light generates electricity by creating a charge imbalance after knocking electrons out of atoms from semiconducting materials.

Charging an EV depends on power source, charger type and battery size

It takes less time to charge an electric vehicle's battery for Level 3 chargers, which can deliver 80% capacity in as little as 30 minutes. Level 1 chargers can take days. Larger vehicles possess larger batteries that increase charging time, despite often having less range.

Batteries range in size based on their purpose, cost, and manufacturability

Lead-acid batteries used in combustion vehicles are resilient to temperature extremes, low-cost, and provide high surge current, which is needed for initial ignition. Alkaline batteries, including AA, AAA, and B, have long shelf lives and supply the low, steady power required for electronics with minimal demand fluctuations.

Electrogenic animals generate their own electricity within an electric organ by changing the pattern of electrical charges in disc-shaped cells called electrocytes.

Lightning storms are more common in coastal and tropical regions

Water-abundant areas that receive increased solar radiation, such as those near the equator, experience increased rates of evaporation, which produce tall clouds as moisture rises, cools, and condenses. Mountain ranges can also steer air to higher altitudes, creating collisions between atmospheric particles that generate charge imbalances—the precursors to lightning.

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.

Named after Nikola Tesla, who pioneered alternating current power systems, the Tesla coil was the first device to wirelessly transmit electricity.

Simulate the build-up and discharge of static electricity with 'John Travoltage.'

Tesla's first successful AC prototype used a metal shoe polish tin for a rotor

After leaving his position working with Thomas Edison, Tesla partnered with George Westinghouse to promote alternating current systems as a more viable, scalable solution to electricity transmission.

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.

Being near a lightning strike—even without getting struck—can be fatal

Because animal tissue is generally more conductive than soil, electricity moving along Earth's surface after a strike tends to travel up and back down an animal's legs, discharging dangerous amounts of energy along the way, with risks increasing the farther apart the legs are. This ground current accounts for about half of all lightning-related deaths and injuries in humans.

The history of the North American power grid, which is composed of five major grids

Thomas Edison's Pearl Street Station was the first US commercial power plant, burning coal to power lamps for some Manhattan residents. Over time, local power plants would be bought out by larger ones, forming interconnected systems spanning multiple states. Today, the Eastern Interconnection and Western Interconnection are the largest of these systems.

Which countries have the fastest internet speeds?

Ever wonder about how fast internet speeds are around the world? Take a look at this graphic which lists out the countries with the highest mobile internet speeds in 2023. Countries in the Middle East and East Asia dominate the list while America lags behind in eighteenth place. Learn more about why a high-income country like the US fall behind in speed, and why other countries are internet powerhouses.

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.

Before the invention of transistors, vacuum tubes made radio possible

Discovered by Thomas Edison, vacuum tubes allow electrical currents to travel through empty space. Later modified into a diode—keeping current flowing in only one direction—vacuum tubes allowed electronics to turn alternating current into direct current.

As much as 10% of home electricity use comes from unused devices left plugged in.

How cosmic rays and pointed ice shards help generate lightning in clouds

Although clouds generate electric fields as electrons are transferred when currents move past one another—not unlike building up static electricity by rubbing socks against carpet—these fields have been measured to be a tenth of the strength needed to make electricity strong enough to travel through air. However, pointed crystals are estimated to boost fields by factors greater than 10, and particles from outer space may help initiate cascades of displaced electrons.

Most data centers rely on the local power grid to feed power-hungry computer equipment

These facilities house rows of vertical racks containing multiple types of hardware, including servers that provide 24/7 access to online applications, services, and data. In a hyperscale center with thousands of these racks, the annual electricity used is estimated to equal that of 400,000 electric vehicles.

Ranking the most expensive appliances on your electricity bill

Energy costs have gone up amid war and inflation. Here's a breakdown on the cheapest and most expensive appliances in your home to help you lower your bill.

For the same cost, turbines with three blades are the most resilient

Odd-numbered blade values more evenly distribute wind loads across the face of rotors, reducing bending and twisting forces on the turbine that cause wear. Modeling shows that three blades optimize efficiency and cost for everyday wind speeds.

As of 2025, about 9 in 10 Americans use the internet daily

Polling finds that while most Americans have home broadband and smartphones, digital divides persist. Young adults, Hispanic adults, and lower-income households are significantly less likely to subscribe to home broadband and more likely to rely on smartphones as their primary means of internet access.

Nearly 40% of American cars were electric in 1899

They were most common in cities, where battery swap stations allowed drivers to "refuel" their vehicles reliably. Innovations in combustion engines caused electric cars to lose ground until environmental policies and advances in battery technology revitalized interest.

Learn why electrical substations are needed to provide safe electricity with minimal energy loss

These typically fenced-off facilities with steel boxes or cylinders topped with cone-like caps house circuit breakers, fuses, and switches that can isolate sections of the grid to prevent electrical failures from spreading. Substations use transformers to modify electrical voltage and are customized to the generation, transmission, and distribution networks they interconnect.

Electric vehicles have been around since the 19th century

The first EVs ran on rechargeable lead-acid batteries, which could travel 60 to 80 miles on a single charge. Women preferred these vehicles, which were quieter, less smelly, and did not require turning a hand crank to start the engine.