50 Fun Facts About Electricity

The word 'electricity' derives from 'elektron', the ancient Greek word for what?

William Gilbert coined 'electricus' in 1600 for the way rubbed amber attracts light objects; Thales had noted the effect around 600 BCE.

Whose 1600 book De Magnete first carefully separated static electricity from magnetism?

Before Gilbert, electricity had been little more than a curiosity for two thousand years.

Benjamin Franklin is said to have flown a kite in a storm in June 1752 with what tied to the string?

Sparks jumping from the key to his hand showed lightning was electrical; his son William reportedly helped, and the key was borrowed from Benjamin Loxley.

A scientist attempting to replicate Franklin's experiment in St Petersburg in 1753 was killed. Who?

He is thought to have been struck by ball lightning; Dalibard had safely done the rod version in France a month before Franklin's kite.

Luigi Galvani discovered in 1780 that the legs of dead frogs did what when touched by an electric spark?

His 'animal electricity' theory was challenged by Volta, but it gave us the words galvanise and galvanic and inspired Mary Shelley's Frankenstein.

Volta's 1800 voltaic pile was made from alternating discs of copper and which other metal?

It gave scientists a steady current for the first time and proved electricity could be made chemically; Napoleon was an admirer.

Besides inventing the battery, Volta is credited with discovering which gas?

He held the chair of experimental physics at Pavia for nearly forty years, and the volt is named after him.

In 1820 Hans Christian Ørsted noticed, while preparing a lecture, that an electric current did what?

The accidental discovery linked electricity and magnetism; Ørsted was also the discoverer of aluminium and a friend of Hans Christian Andersen.

Michael Faraday invented the electric motor in which year?

A former bookbinder's apprentice hired by Humphry Davy, he went on to discover electromagnetic induction, the basis of every generator.

Which everyday electrical terms did Faraday help popularise?

He also discovered benzene, built an early Bunsen burner and had Einstein's admiration; the farad, the unit of capacitance, bears his name.

Ohm's law is usually written as V = IR. What does the R stand for?

Georg Ohm published his analysis in 1827; current is directly proportional to voltage in a well-behaved conductor.

The ampere is named after a physicist from which country?

André-Marie Ampère is considered a father of electromagnetism alongside Ørsted; since 2019 the amp has been defined by fixing the elementary charge.

The SI unit of power, the watt, honours James Watt for his improvements to what?

Watt also developed the concept of horsepower; the unit was adopted by the British Association in 1889 and by the SI in 1960.

James Clerk Maxwell definitively linked electricity, magnetism and what else in the 1860s?

His equations remain the basis of all modern electromagnetic theory; Einstein kept his portrait beside Faraday's and Newton's.

By historical convention, electric current is defined as flowing in which direction?

Franklin set the convention long before electrons were discovered, so 'conventional current' runs opposite to the actual electron flow.

The electron was discovered in 1897 by which physicist, working with cathode rays?

The name 'electron' had already been proposed by George Johnstone Stoney in the 1870s and 1890s.

The electric field driving electrons through a wire propagates at close to what?

That is why an electrical signal reaches the far end of a cable almost instantly even though individual electrons crawl.

Among pure metals at room temperature, which alone conducts electricity better than copper?

Copper's softness partly explains its conductivity; it is used for most wiring because silver is far too expensive.

What is the name for charge transfer through rubbing, which explains static shocks from doorknobs?

Rubbing transfers electrons between materials; a balloon rubbed on hair goes negative and clings to a wall.

The air around a lightning flash heats to roughly what temperature?

That sudden heating creates the shock wave we hear as thunder.

Roughly how many lightning flashes occur on Earth per second, on average?

That works out to nearly 1.4 billion flashes a year; Lake Maracaibo in Venezuela sees the most, with about 250 bolts a day.

Where on Earth does lightning occur most often, with the Catatumbo phenomenon producing about 250 bolts a day?

Most cloud-to-ground strikes are 'negative'; positive flashes make up under 5% but are more powerful.

Electric eels can deliver shocks of up to roughly how many volts?

Despite the name they are knifefish, not true eels; in 2019 they were split into three species, one named Electrophorus voltai after Volta.

Thomas Edison's first commercial power plant, Pearl Street Station, opened in 1882 in which city?

It began with six 100 kW dynamos serving 400 lamps for 82 customers in Manhattan's financial district and ran the world's first underground urban network.

How many US patents did Thomas Edison register?

The 'Wizard of Menlo Park' ran what is considered the first industrial research laboratory and became deaf as a child.

Edison's team found a carbonised filament of which material could burn for over 1,200 hours?

His November 1879 patent listed cotton, linen and wood splints; Joseph Swan's bulbs were already lighting London by 1881, and tungsten came later.

Roughly what share of the energy an incandescent bulb uses becomes visible light?

The rest is heat, which is why LEDs have taken over most of the market.

In the 'war of the currents', which industrialist backed AC against Edison's direct current?

His company licensed Tesla's induction motor patents in 1888 and won the contract to light the 1893 Chicago World's Fair.

The 1892 merger of Edison's company with its biggest rival created which corporation?

Edison Electric merged with Thomson-Houston, effectively ending the war of the currents; the last DC utility in New York City was not switched off until 2007.

Nikola Tesla was born in 1856 in Smiljan, a village in what is now which country?

An ethnic Serb, he briefly worked for Edison in New York before licensing his AC patents to Westinghouse.

The tesla, named in Nikola Tesla's honour in 1960, is the SI unit of what?

His work had fallen into obscurity after his death in a New York hotel in 1943; his unfinished Wardenclyffe Tower was meant to transmit power wirelessly.

Tesla built one of the first wirelessly controlled vehicles ever produced. What was it?

He demonstrated it in 1898; he also experimented with X-ray imaging and dreamed of worldwide wireless power from Colorado Springs.

Superconductivity was discovered in 1911 in which element cooled by liquid helium?

Heike Kamerlingh Onnes made the discovery in Leiden; 'high-temperature' ceramic superconductors followed in 1986.

Which country runs its power grid on two different frequencies, 50 Hz in the east and 60 Hz in the west?

Tokyo is on 50 Hz and Osaka on 60 Hz, a legacy of buying German and American generators in the 1890s.

Standard household outlets in North America supply roughly what voltage?

The split-phase system also offers 240 V for big appliances; the low voltage is one reason electric kettles are rare in the US.

The Northeast blackout of August 2003 left about how many people without power?

A software bug in FirstEnergy's Ohio control-room alarm system meant operators did not see overloaded lines sagging into trees.

The Hoover Dam, built between 1931 and 1936, sits on which river?

It straddles the Nevada-Arizona border and created Lake Mead; Franklin Roosevelt dedicated it in September 1935.

Which pair discovered in 1800 that current from a voltaic pile could split water?

Faraday greatly extended the work in 1833 and formulated the laws of electrolysis.

Which English physicist, remembered in the unit of energy, studied resistive heating of wires in 1840?

Joule heating is what makes toasters, kettles and incandescent bulbs work.

The unit of electric charge honours which 18th-century French physicist?

Coulomb's law gives the inverse-square force between charges; one amp is one coulomb of charge per second.

Alternating current reverses direction repeatedly, almost always following what waveform?

Its time-averaged value is zero, yet it delivers energy first one way then the other; batteries and most electronics use direct current instead.

Humphry Davy made an early incandescent light in 1802 by passing current through a strip of which metal?

The battery had 2,000 cells in the basement of the Royal Institution; platinum was chosen for its very high melting point.

Which former Edison employee patented an improved way of making carbon filaments in 1882?

The African American inventor's process was bought by the United States Electric Light Company and gave rival Maxim bulbs their distinctive M-shaped filaments.

Which Greek philosopher studied static electricity by rubbing amber rods around 600 BCE?

He wrongly believed the friction made the amber magnetic, like the mineral magnetite.

How did Benjamin Franklin fund his extensive electrical research?

His June 1752 kite experiment reputedly showed sparks jumping from a key to the back of his hand.

Franklin defined positive charge as the charge acquired by a glass rod rubbed with what?

By modern convention electrons are negative and protons positive, each carrying exactly the elementary charge.

Roughly what current is the threshold for a person to perceive mains-frequency electricity?

Under some conditions a current as low as a microamp can be felt as an electrovibration effect.

Piezoelectricity, in which pressed crystals such as quartz generate a voltage, was discovered in 1880 by whom?

The effect works in reverse too: an electric field makes the material change size slightly. Even sugar is piezoelectric.

Modified muscle cells that let electric eels generate high voltages are called what?

Sharks, by contrast, are electroreceptive: they detect electric fields rather than generate them as weapons.

Where does a hollow conducting body carry all of its electric charge?

The field inside is therefore zero, which is the operating principle of the Faraday cage.