Story Of Electricity - The Greeks To Franklin (1968)

[Music] thank you [Music] more than 2500 years ago the ancient Greeks noticed that if a piece of Amber were rubbed it would attract bits of straw or other light objects the Greeks knew of another mineral they called magnet that attracted objects but somewhat differently magnet didn't attract the bits of straw the Amber did even when rubbed [Music] but Magna did attract iron and it would do this even when it wasn't rubbed the Greeks thought these two attractions were related and tried to explain them one explanation involved invisible atoms of which everything was made 2500 years ago Democritus suggested that these atoms go out from the magnet and return to it pulling the attracted things back 1500 years later men discovered a use for one of these effects the mineral magnet tended to line up in a north-south direction and so was useful in telling directions but the Amber effect remained just a curiosity for 400 more years until an English physician William Gilbert suggested in 1600 that magnetism and the Amber effect were actually quite different he invented an instrument which he called a versorium and described it make yourself a visorium of any medal you like three or four fingers long resting rather lightly on a point for support bring up to one end of it a piece of Amber and the visorium turns immediately many things are seen to attract not just Amber hard ceiling wax diamond Sapphire opal sulfur and even glass Gilbert called all these materials electrics and Define them as things that attract in the same manner as Amber how something must flow out from Amber when it is rubbed like invisible rods which seize and draw lightweight objects after two thousand years men were at last beginning to study the Amber effect separately from magnetism Gilbert enlisted glass as an electric and soon other scientists began using it in their electrical experiments in 1732 another Englishman Stephen gray announced a new discovery about Electrics the first experiment I made was to see if I could find any difference in the tube's attraction when it was stopped at both ends by corks but upon holding a down feather near the upper end of the tube I found that it would go to the cork being attracted by it just as it was by the tube itself gray was the first person to observe that the Amber effect the ability to attract could be transferred from one object to another touching it experimenting he discovered this ability could be transferred greater and greater distances he added a stick and an ivory ball to the cork tube and the attractive property somehow moved from the glass tube to the Ivory ball he increased The Distance by using string instead of a stick he used metal foil instead of feathers and it too was attracted to the Ivory ball I then made several attempts to pass this electric property along a horizontal line but not the least sign of attraction was perceived I concluded that when the electric property came to the loop it went up the same to the ceiling so that none or very little of it came down to the ball a friend proposed a silk cord I told him that this support might do better on account of its smallness for then there would be less of the electric property carried away this time when the electric property was produced by rubbing the tube it got to the Ivory ball gray continued extending the length of the line 80 feet 300 feet 600 feet but now the silk supporting threads began to break under the weight of the long line and they were replaced by support wires made of brass but though the tube was well rubbed this time nothing happened and so Stephen gray discovered something else it wasn't the size of the support cord that was important it was the material substances like silk thread transmitted this electrical ability poorly substances like the brass wire transmitted it well after Gray's Discovery scientists began to speak of some invisible substance moving along these conductors and from Gilbert's word electric they call this invisible substance electricity meanwhile another Englishman Francis hawksby had invented a machine to take the drudgery out of electrical experimentation the glass globe on hawksby's machine could be spun rapidly by means of a crank the rubbing was done just by resting the hand on the spinning globe later experimenters even managed to eliminate the hand a leather pad did the actual rubbing electricity produced by this rubbing would flow up wires to a metal collecting rod on this machine it's a sword and from there it could be made to jump across a small Gap to a person's hand making a spark the next question was could this electricity be stored somehow two men independently arrived at the same idea and tried storing it in a flask of water one of them was a Dutch professor of mathematics Peter Van mussenbrook who lived in the town of Leiden I am going to tell you about a new but terrible experiment which I advise you not to try for yourself electricity from the spinning globe of a hawksby machine was communicated by chains to a gun barrel from the other end of the Gun Barrel there hung a brass wire which passed into a glass flask partially filled with water with my left hand I attempted to draw Sparks from The Gun Barrel my right hand was struck as if by lightning Peter Van musenbrook of Leighton had painfully discovered how to store a large amount of electricity in a jar of water later experimenters learned water wasn't necessary electricity could be stored in an empty glass vessel if it were covered inside and out with metal foil and after the town in which it was discovered they call this a Leiden jar meanwhile in the American colonies another man began experimenting your kind present of an electric tube with directions for using it has put several of us on making electrical experiments I never was before engaged in any study that so totally engrossed my attention and my time the writer of this letter was Benjamin Franklin in 1747 as Franklin began his studies men already knew that electricity could be produced by rubbing certain kinds of materials together that it could be transferred to other objects that it could be collected in a Leiden jar and that it had attractive properties but they also believed there were two different kinds of electricity a few months later Franklin suggested the theory that there is only one kind of electricity and he described an experiment to illustrate that theory if a were to stand on wax and rubber glass tube he will put electrical fire from himself into the glass since his communication with the common stock of electrical fire in the world is cut off by the wax insulator his body will then have a deficiency of electrical fire if B likewise stands on wax when he passes his knuckle along near the tube he will receive the fire which was collected by the glass from a since B's communication with the common stock is likewise cut off by the wax he will retain the additional quantity of electrical fire he received Franklin's idea was that there is only a single electrical fluid the man with a glass tube would now have less than the normal amount of it the man who had touched it would have more but they would both seem electrified to a third man who wasn't insulated from the ground by the wax blocks and therefore has just a normal amount of electrical fire he would receive a spark from the man who had the over quantity and give a spark to the man who had the under quantity but in both cases according to Franklin the electrical fire was the same thing further Franklin was convinced that the tiny spark created in the laboratory was different only in size from the violent lightning [Applause] and he devised an experiment to demonstrate it using a wire attached to the top of a kite the kite is to be raised when a thunder gust appears to be coming on to the end of The Kite string Franklin tied a key then a silk ribbon to insulate himself from the kite string you must stand in a door or window so that the silk ribbon may not be wet from rain as soon as any of the thunder clouds come over the kite the pointed wire will draw the electric fire from them and the kite will be electrified and when the rain has wet the kite and Twine it will stream out plentifully from the key on the approach of your knuckles the electrical fire from the cloud can be stored in a Leiden jar just as the electrical fire from a glass tube can and all electrical experiments can be done with either one that by the sameness of the electric matter with that of lightning is completely demonstrated it had taken 2300 years to write the first chapters in the story of electricity from this point on the story raced forward [Music]