E is for Electricity

By Siobhan Fairgreaves

Last time, in D for Detectors, we looked at some of the applications of physics that you might encounter during your day. In this post, we’re going to find out more about something I can guarantee you use almost every day- electricity!

Far from simply being a piece of tack on your ‘cool’ uncle’s shelf, the plasma lamp is one of the best ways to see¬†electron flow ¬†in action

A reliable source of electricity is something we could easily take for granted, but how does it actually work? Well, surprise surprise, it all comes back to our friend- the humble atom. More specifically, electricity is the flow of electrons – remember them?

Electrons are the tiny negatively charged subatomic particles which whizz around the outside of the nucleus. In some materials, such as copper, the outer electrons break off quite easily and their movement through the material (a copper wire for example) creates an electric current.

Of course, not all materials can conduct electricity. I’m sure you remember the experiment in school where you tried to complete a circuit with different materials- they didn’t all work. Rubber, for example, holds onto its electrons pretty tightly so they can’t easily flow. This means rubber can’t conduct electricity.

Now back to that circuit experiment you may have tried. Your copper wires alone aren‚Äôt enough to light the bulb- you also need a source of power, like a battery.¬† The battery is a source of ‚Äúpushing power‚ÄĚ to move the electrons along. The official name for this is the electromotive force (EMF) but it‚Äôs more commonly known as voltage.

Ah, the good old Mexican current… at least that’s what it’s called among scientists who¬†advocate Mexican wave-particle duality¬†| Image: Martin Thomas

One way of thinking about electricity is a bit like a Mexican wave in a stadium. It usually takes a few people acting together to get it started- that’s the battery, and then the wave (or energy) transfers through each person and onto the next. The moving wave is a bit like the moving electrons.

Time for a fun fact now- did you know that the band AC/DC can actually teach us more about electricity? Their name came from seeing a symbol on their sisters’ electric sewing machine. This symbol stood for Alternating Current/Direct Current and meant that the machine could work with either type or electrical current.

“I’m on the hiiiiiiighwaay to… oh yeah, I’m periodically changing direction, so I guess I’m not really going anywhere” – an electron in an AC power line

Direct Current is best explained by the Mexican wave analogy used above. All the electrons move in the same direction. This type of current is used in toys and small gadgets. Larger machines tend to require Alternating Current.

The electrons forming an Alternating Current reverse direction 50 to 60 times a second. It’s a bit difficult to imagine how that could create a current but remember it’s all about transfer of energy. The battery still provides the initial push but these electrons don’t run in a straight line, they run on the spot instead. It doesn’t work in quite the same way but, just like Direct Current, still requires loose electrons and they still need energy.

See you next time for a convenient start of summer post- F for Flying!

F is for Faraday

By Jonathan Farrow from The Thoughtful Pharoah

The year is 1791. ¬†On a crisp autumn morning in South London, Margaret Hastwell, a blackmith’s apprentice, gives birth to her third son. ¬†With her husband, son, and daughter crowded around, she decides to name the newborn¬†Michael. ¬†Michael Faraday.

Margaret had a lot on her plate, what with two young children, a husband who was often sick, and quite a few bills to pay. ¬†She probably didn’t have much time or energy for idle thought or daydreaming. ¬†I doubt if she much considered what Michael might do with his life other than get by. ¬†There is no way it occurred to her that Michael would grow up to revolutionize the world of physics, make electricity a viable source of mechanical energy, and inspire countless scientists, engineers, and young people (including but not limited to Einstein, Rutherford, and this young science communicator, 223 years later). But that is exactly what he would do.

Faraday went to elementary school and learned to read and write, but by the time he turned 13, he had to start work in order to help his parents make ends meet. ¬†He was apprenticed to a local bookbinder and spent the next 7 years diligently mending books. ¬†But that wasn’t all he was doing. ¬†He was also reading. ¬†Over those 7 years, Faraday read voraciously and became interested in science, particularly the topics of Chemistry and Electricity. Luckily for him, George Riebau, the bookbinder to whom he was apprenticed, took an interest in young Faraday’s education and bought him tickets to lectures by¬†Humphry Davy¬†at the Royal Institution in 1812. ¬†This was only¬†shortly after Davy had¬†discovered calcium and chlorine through electrolysis. ¬†Davy was a big name in science¬†at the time, comparable to today’s Stephen Hawking, Neil Degrasse-Tyson, or Jane Gooddall, so it was with wide eyes that young Faraday attended. ¬†He was so blown away by what he saw and heard that he faithfully wrote notes and drew diagrams. ¬†These meticulous notes would prove to be his ticket into Davy’s lab.

Davy Notes
“I got a golden ticket!” Image from the Royal Society of Chemistry

Later that year, Faraday sent a letter to¬†Davy asking for a job¬†and attached a few of his notes. ¬†Davy was impressed and so interviewed young Faraday, but ultimately rejected the eager young fellow, saying “Science [is] a harsh mistress, and in a pecuniary point of view but poorly rewarding those who devote themselves to her service.” ¬†Translation: ¬†“Sorry, I don’t have space for you in my lab, but just to let you know… Science really isn’t very profitable.” ¬†A few months later, one of Davy’s assistants got in a fight and was fired, so guess who got a call? ¬†That’s right, Mikey F.

Not only did Faraday get a spot in Davy’s lab, but he also got to go on a European¬†tour with Mr. and Mrs. Davy. ¬†Pretty sweet deal, right? ¬†On the eighteen month journey, Faraday got to meet the likes of Amp√®re and Volta. ¬†If those names are ringing distant bells, it should be no surprise. ¬†Those eminent continental scientists give their names to standard units of electrical current¬†(Ampere)¬†and potential difference¬†(Volt). ¬†Re-invigorated, 22-year-old Faraday returned to London and took up a¬†post at the Royal Institution as Davy’s assistant.

The next two decades saw Faraday make great advances in chemistry, including discovering benzene, liquefying gases, and exploring the properties of chlorine. ¬†He didn’t get much chance to focus on electricity, however, until 1821. ¬†In that year, Faraday started experimenting with chemical batteries, copper wire, and magnets. ¬†Building on the work of¬†Hans Christian √ėrsted, Faraday’s¬†work was some of the first to show that light, electricity, and magnetism are all inextricably linked (we now know that they are all manifestations of the electromagnetic force). He was a dedicated experimentalist and between 1821 and 1831, he effectively invented the first electric motor and, later, the first electric generator. ¬†These two inventions form the basis for much of today’s modern power system. ¬†The electric motor that opens your garage door as well as wind and hydro-electric generators work on the exact same principle that was discovered by Faraday back in 1831: electromagnetic induction.

Faraday’s insight was that when connected¬†by conductive material, an electric¬†current could make¬†a magnet move. ¬†He also found that the reverse was true: a moving magnet can¬†create a flow of electrons: an electric current.¬†The experiment is actually quite simple and you can even¬†try it at home. Induction enables the transformation of energy between¬†mechanical, electrical, and magnetic states. ¬†Before Faraday, electricity was seen simply as a novelty. ¬†Since Faraday, we’ve been able to use it for all sorts of things. ¬†Like writing science blogs!

The famous iron ring experiment.  Two insulated coils of wire are wrapped around an iron ring but kept separate.  Attaching one to a battery will create a momentary current in the other.  Induction!
The famous iron ring experiment. Two insulated coils of wire are wrapped around an iron ring but kept separate. Attaching one to a battery will create a momentary current in the other. Induction!   Image by Eviatar Bach

[While he was definitely a gifted scientist, Faraday knew next to nothing about mathematics. ¬†He observed, took careful notes, and had an intuition for how to design experiments, but could not formalize his theories in mathematical language. ¬†He would have to wait for James Clerk Maxwell, a young Scottish¬†prodigy, to do the math and formalize¬†Faraday’s Law¬†in the 1860s.]

Faraday continued his work on electricity and gained all sorts of recognition, including medals, honorary degrees, and prestigious positions.  This increased pressure may have been to blame for a nervous breakdown in 1839.  He took a few years off, but by 1845 he was back at it, trying to bend light with strong magnets.  He discovered little else after the 1850s, but continued to lecture and participate in the scientific community.

Older Faraday with glass bar
While that does look remarkably like a cigar, Faraday is actually holding a glass tube in his hand. A glass tube… of Science! ¬† ¬†Public Domain image from Wikimedia

So not only can Faraday be considered to be one of the fathers of the modern world because of his breakthroughs in electricity, but he can¬†also be considered to be one of the fathers of modern popular science communication. ¬†In 1825, he decided to give a series of Christmas lectures at the Royal Institution, specifically aimed at children and non-specialists. ¬†He gave these lectures every year until his death in 1867 and was renowned as a charismatic, engaging speaker. ¬†He tried to explain the science behind everyday phenomena and in 1860 gave a famous lecture on the candle, something which everyone had used but which few actually understood. ¬†The¬†Christmas lectures continue to this day and, continuing with Faraday’s legacy, the Royal Institution is one of the UK’s leading science communication organizations.

Doesn't that look fun!?
Doesn’t that look fun!? ¬† ¬†Public Domain image from Wikimedia

It is not simply that Faraday was a great scientist and lecturer, nor that he managed to escape poverty in 19th century England to become world-renowned. ¬†Michael Faraday’s story is so¬†great¬†because by all accounts, he deserved every bit of success he gained. ¬†One biographer, Thomas Martin, wrote in 1934:

He was by any sense and by any standard a good man; and yet his goodness was not of the kind that make others uncomfortable in his presence. His strong personal sense of duty did not take the gaiety out of his life. … his virtues were those of action, not of mere abstention

It’s no wonder that Einstein had a picture of him up in his office. ¬†I think I might just print one off myself.

Faraday painting 1842
Still pretty handsome considering this painting is from 1842, making Faraday 51 years old.   Public Domain image from Wikimedia