A Kite, a Key and a Flash of Lightning - The Chemistry of Electricity

published before 1923 and
public domain in the US.

Everyone has heard the story of Ben Franklin and his Kite. In June 1752, as the legend goes, Franklin flew his kite in a thunderstorm with a key tied to a silk string used as the tether. He then waited for lightning to strike! If this is how it really happened, it probably would have been good Ben's last experiment. But it wasn't. He wrote very little of this test, in spite of his prolific library of tomes. One such letter, written on October 19, 1752 to Peter Collinson, a fellow scientist and friend in London, was discussing how he built his kites.

Franklin wrote:

"Make a small cross of two light strips of cedar, the arms so long as to reach to the four corners of a large thin silk handkerchief when extended; tie the corners of the handkerchief to the extremities of the cross, so you have the body of a kite; which being properly accommodated with a tail, loop, and string, will rise in the air, like those made of paper; but this being of silk is fitter to bear the wet and wind of a thunder gust without tearing. To the top of the upright stick of the cross is to be fixed a very sharp pointed wire, rising a foot or more above the wood. To the end of the twine, next the key may be fastened.

This kite is to be raised when a thunder-gust appears to be coming on, and the person who holds the string must stand within a door or window, or under some cover, so that the silk ribbon may not be wet; and care must be taken that the twine does not touch the frame of the door or window. 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, with all the twine, will be electrified, and the loose filaments of the twine, will stand out every way, and be attracted by an approaching finger. And when the rain has wetted the kite and twine, so that it can conduct the electric fire freely, you will find it stream out plentifully from the key on the approach of your knuckle. At this key the phial may be charged: and from electric fire thus obtained, spirits may be kindled, and all the other electric experiments be performed, which are usually done by the help of a rubbed glass globe or tube, and thereby the sameness of the electric matter with that of lightning completely demonstrated."

There also is an account written by Joseph Priestley, published fifteen years afterwards but reviewed by Franklin before it was printed. In that account he flew his kite from inside a shed to protect him from the rain. The storm was just moving in and he could see the loose threads of the string standing erect. The he put his knuckle to the key and felt the sharp zap of the gathering static electricity. As the string got wet, more electric fire descended to the key and was collected in a Leyden Jar. Lightning never struck the kite and the experiment was complete before lightning ever appeared.

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Benjamin Franklin was a Prolific Writer
A Dynamic Statesman and
An Inquisitive Scientist

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Franklin was investigating whether or not lightning was an electric phenomenon. He did not discover electricity, as some believe, as it was already known. However, in Franklin's day, the largest man-made sparks were under an inch long. Lightning was a whole lot bigger and more powerful! Franklin realized that if lightning was electricity, then it must be an awful lot of the stuff, and that it would take a long time to amass in the storm. Therefore he suggested to fly the kite early in the storm before the lightning comes near you. After his famous incident, several other would-be-scientists who performed this same kite experiment did not heed his warning and were electrocuted.

Job 28:26 (NLT) - He made the laws for the rain and laid out a path for the lightning.

Franklin was fascinated with electricity and performed many experiments with lightning rods and Leyden Jars, which he grouped together as a type of battery. He even coined numerous terms to describe his work. Franklin wrote Collinson in another letter saying: "I feel a Want of Terms here and doubt much whether I shall be able to make this intelligible." Not only did Franklin have to postulate his theories, he also had to create a new language to fit them. Some of the electrical terms which Franklin coined during his experiments include:

• battery
• charge
• condenser
• conductor
• plus
• minus
• positively
• negatively
• armature

And they are terms we still use today.

Franklin's work confirmed that the electricity in lightning is static electricity, much like what you feel when you rub your shoes on the carpet. The static generates a current that creates sparks that can jump from clouds to the ground, your shoes to the carpet or will make your hair stand on end.

In most common electrical systems, such as the wiring in our homes or our cars, the electricity doesn't come from lightning and is conducted through a metal wire, not a wet string. Metals conduct electricity because of their structure. If you take a block of any metal, it would be made up of a lattice of atoms surrounded by floating electrons that should have been in the atoms outermost electron shell. The metal atoms are so large that the outer electron shell is very far away from the nucleus. Normally the positive charge in the nucleus pulls the electrons into a cloud around it. But since the distance between the nucleus and the negative electrons is very high, the strength of attraction between them is so weak that the electrons move out of the orbit and into a sea of electrons around all the atoms of the metal. The electrons are said to be de-localized. Thus metals are sometimes referred to as "an array of positive ions in a sea of electrons."

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Conducting Metals are sometimes referred to as
"An Array of Positive Ions in a Sea of Electrons."

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This sea of electrons carries a negative charge. With no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there is zero net current within the metal. When an electric current is applied to one end of any metallic body, these electrons take the electric charge up and carry it to the other end. That is how metals conduct electricity. The best conductors are the Group 11 elements. Silver is the best conductor, followed by copper then gold. (For more on these metals see "Transition Metals", "The Biblical Metals" and "Are Those Metals Really Precious?")

Job 28:15 (NIV) - It [Wisdom] cannot be bought with the finest gold, nor can its price be weighed in silver.

Typically, electric charges in solids flow slowly. For example, in a 20 AWG copper wire, carrying a current of 5 amps, the drift velocity of the electrons is on the order of a millimeter per second. In the near-vacuum inside a cathode ray tube, the electrons travel at about a tenth of the speed of light. In-spite of this slow movement of the electrons, the current is instantaneously established throughout the wire. Think of pedaling a bicycle. The instant you push on the pedal, the chain starts to move the back wheel. Or what about pushing on one end of a long stick, the other end starts to move immediately when you push. The same is true for the electric current. By definition the current flows to the positive so the electrons in the wire are flowing in the opposite direction as the current.

Plasma Lamp - Luc Viatour/ www.Lucnix.be

Electric current is the flow of an electric charge through a carrier. This charge is typically transported by moving electrons in a conductor such as a wire. It can also be carried by positive ions in an electrolyte solution (think batteries), or by both ions and electrons in a plasma. The rate of flow of an electric charge is measured in amperes or amps. An ammeter is used to measure the current.

Several everyday electrical terms we hear in addition to amps are volts, watts and ohms. We use 60 watts bulbs in our lamps, our homes are wired for 120 volts, our cars use 12 volt batteries with 525 cold cranking amps for sure starts and we might have to worry about ohms when we are setting up the speakers in our new home theater system. We will take a closer look at electric current and the relationship of these terms in the next blog.

Psalms 119:105 (NLT) - Your word is a lamp to guide my feet and a light for my path.