How did Michael Faraday make electricity with magnets? Hey, how does anyone make electricity with magnets? And what does that have to do with the creation of the idea of magnetic fields? Watch this short video and find out. Ready? Let’s go.
In 1826, an English scientist named Michael Faraday had read that another Englishman named William Sturgeon had made a pretty strong magnet by wrapping wire around an iron bar and putting current in the wire. Sturgeon had used iron that was coated in lacquer and bare wire. Because of this, Sturgeon had to be careful that the wires didn’t touch, or the electricity would just short circuit across the wires instead of through the wires.
Faraday had a little 6-inch iron ring that wasn’t coated. He decided to wrap the wires with a cloth to insulate them instead of coating the iron. In this way, he could wrap the wires very close together and make a much stronger electromagnet. Because his iron was a ring, Faraday wrapped two separate coils, one on the left side of the ring and one on the right. It looks like a strange artifact from a mummy’s crypt. Faraday used to keep this ring in his pocket while he did other research. He was sure that it would be useful somehow, he just didn’t know-how.
Then on August 29th, 1831, Faraday took a professional risk. He quit his government research job that he hated and decided to branch out on his own. What Faraday wanted to do was study electricity and magnetism. Specifically, Faraday was determined to create electricity with a magnet. After all, it had been eleven years since a Danish man named Hans Ørsted had shown that electricity pushes magnets, it seemed logical that magnets must affect electricity. For many years he had been tinkering with magnets and wires but to no avail. He wondered if maybe the magnet wasn’t strong enough. For that reason, he took out his little ring from his pocket.
Faraday decided to use one side of the ring as his magnet and the other side as his “tester” to see if he could create current without directly connecting to a battery.
He put a compass under the tester wire to see if it had any current.
When Faraday connected a battery to the first coil an amazing thing happened, the magnet next to the second coil twitched. Then, nothing. When he cut off the current the magnet twitched again, in the other direction! Then, nothing again. Faraday repeated this experiment multiple times and found that he created a current in the second wire when the first one was charging up or discharging but never when it was flowing steadily, even when it had an incredibly large current. In other words, an electro-magnet only creates current when the magnet was changing, if its strength is steady nothing happens.
Faraday wrote to a friend about his accomplishment, “I am busy just now again on Electro-Magnetism and think I have got hold of a good thing but can’t say; it may be a weed instead of a fish that after all my labor I may, at last, pull up.” He had managed to use electricity to create electricity but he still hadn’t managed to use magnets to create electricity. After several attempts that were (mostly) too subtle to be observed, Faraday pushed a very strong magnet into a coil of wire and retrieved it again. When the magnet was moving, the compass moved too. Here was the “fish” that Faraday was hoping to catch! He had, briefly, created electricity with magnets and motion.
Faraday had another device at his disposal. The Royal Institute where he worked had a giant magnet (actually 437 magnets stuck together) that Faraday could play with. Faraday placed an iron bar on the great magnet, therefore making the bar a strong magnet. Moving a coil towards and away from this bar created a strong current. However, he couldn’t detect a current even from this incredibly strong magnet when the coil was still.
Let’s review Faraday’s discoveries. He created a current in a coil of wire if 1) the coil was moved towards or away from a strong magnet, 2) a magnet was moved towards or away from the coil, or 3) the magnetism of an electromagnet was increased decreased connected to a coil of wire.
Faraday needed a way to describe this new phenomenon. He was a visual thinker with no math skills so he began imagining “magnetic curves” emanating from bar magnets, electromagnets, and current-carrying wires. For centuries people had noticed that if you sprinkle iron filings around a bar magnet, it creates patterns. In his paper Faraday said that the iron filings were lining up with these “lines of magnetic forces” that were always present around magnets and around current-carrying wires, the iron filings just made them visible. In this way, Faraday invented the idea of magnetic fields in 1831! Faraday’s law is that current is created (or induced) when the lines of force are broken or “cut” by a coil of wire. Think about pushing the bar magnet into a coil of wire: as you push the magnet the magnetic field lines pass through the coil and induce a current. Faraday felt that it was this disturbance in the force (not to get to star wars about it)that created the current in the coil. As strange as this seems, this is the theory we believe in today!
Faraday realized that the current he had produced was in spurts, he wondered if he could use magnets to make continuous electricity as a battery does. In this quest, he was inspired by something called Arago’s disk. Nine years earlier a swashbuckling Frenchman named Francois Arago had noticed that if a copper disk was rotated near a compass magnet the compass magnet would turn too. Faraday decided that it worked because turning the wheel moved the parts of the disk closer and farther from the magnet, which created a current in the disk. The current then pushes the original magnet.
Faraday tested his hypothesis using the giant magnet at his disposal. He added metal to his large magnet to make a U-shaped magnet. He then placed a copper disk so that it could spin between the poles and connected the disk with a wire to a meter to measure current. When he spun the wheel, the needle turned and stayed constant, Faraday had used motion to create a steady current! He had also invented the first electric generator!
Faraday’s results were astonishing – the scientific community was especially impressed with his solving the mystery of Arago’s disk. Faraday himself felt particularly satisfied to have succeeded without using Math, a subject he didn’t know! He read his work on generating electricity on November 24th, 1831. It was so popular that the prime minister dropped by the laboratory to see Faraday’s generator firsthand. When he asked Faraday about its uses, Faraday supposedly replied, “I know not, but I wager that one day your government will tax it.” (a bet he would win)
Although the generator that Faraday made was impressive for demonstrations, the current would make strange patterns in the disk (called eddy currents) that would keep it from producing large currents. In fact, it would take another thirty years before a cast of characters managed to make a useful electric generator, and that story is next time on The Secret History of Electricity.