By Robert M. Hazen, Ph.D., George Mason University
Did you know that the electrostatic phenomenon was studied by Benjamin Franklin, the great American statesman, who played an important role in drafting the Declaration of Independence, but was best known in his own day as a scientist/physicist. He was called one of the leading ‘electricians’ of his day. That was the title they gave to people who studied the electrostatic phenomena.
The Good and Bad of the Electrostatic Phenomenon
Benjamin Franklin gained great fame as a successful inventor, notably the Franklin stove, and then later the lightning rod. He suggested that the electrostatic charge is a kind of fluid, or what today is called electrons, although Franklin didn’t know that then (discovered a century later). A material becomes charged when friction removes or adds this fluid from one object to another.
A normal object like a comb is balanced and has a neutral amount of this fluid, exactly enough fluid, but if the comb moves through the hair then Franklin wasn’t sure one object or the other, either the comb or the hair, is gaining more of this fluid, and the other’s getting less of it.
And so, each becomes charged—the hair becomes charged, the comb becomes oppositely charged by the transfer of this one kind of fluid, which should be in balance, but in a charged object it’s not. According to Franklin, if there is a comb, charged, and a ball, not charged, at first, the ball is attracted to the comb, but then they touch and both objects are charged, then they repel each other.
The initial attraction is because the ball that’s uncharged has the fluid moving away from the charged comb, so it gets pulled in, and then suddenly it has an excess, and it gets pushed apart. So, the attraction and repulsion are both shown by these two objects.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
Invention of Lightning Rod by Franklin
Franklin recognized that certain materials take and transfer electric charge, and other materials were insulators. And he realized that this knowledge can be applied to protecting lives, hence the invention of the lightning rod. Franklin realized that lightning was a form of electricity (electrically-charged object).
In fact, it’s said that Franklin went out in a thunderstorm with a kite with a metal string to actually prove to himself that lightning had this kind of electrical property. He showed beyond a doubt that lightning was a form of static electricity.
So, there should be a material that would safely conduct that fluid away from houses down into the ground, and prevent houses and other buildings from being hit by lightning, and that’s what the lightning rod did.
It’s just a simple piece of metal and metal wire, which goes from the roof of a house down into the ground, therefore conducting the electrical fluid away from the house. And it was this understanding of the electrical fluid that allowed Franklin to make this great invention.
Learn more about the nature of science.
Charles Coulomb, who lived from 1736-1806, conducted meticulous experiments on electrostatic forces, and he determined the exact force law between two charged objects. Force equals the product of two charges divided by the square of the distance between them. The equation: force equals the constant charge of the first object times the charge of the second object divided by distance squared.
This equation is very much like that for the force of gravity. A force is present only if there are two charged objects—just like in the gravitational force there is a need for two masses. The force is inversely proportional to the distance between the two objects, just like gravity. There’s also a constant there. In the case of the gravitational consonants, the big G, the same sort of thing is true for the electrostatic force.
Learn more about celestial and terrestrial mechanics.
Xerox Machines and Static Electricity
There’s an important technological use of static electricity in everyday life, and that’s the Xerox machine. There is a rotating drum, and that drum is made of special material that takes a static charge. When light shines on part of the drum, that static charge is eliminated, and that part loses its charge completely.
Therefore, if a black-and-white pattern is shined onto the drum, that black-and-white pattern is reproduced in the static charges on the drum. The drum rotates by a pile of very tiny plastic beads, which are, by static electricity, attracted to the charged parts of the drums, but not to the uncharged parts of the drum.
And that black powder, that black plastic, is then impressed onto a piece of hot paper, the plastic melts onto the paper and that’s the Xeroxed copy. So Xerox machines use static electricity in a very basic way. By the way, for a darker copy, the voltage should be turned up to get a higher static charge. For a lighter copy, the voltage should be turned down to get less of that black powder attaching to the drum.
Common Questions about Benjamin Franklin and the Study of Electrostatic Phenomenon
Franklin was a great inventor and became known for the Franklin stove and lightning rod. He also proposed that the charge of the electrostatic phenomenon is a fluid (electrons), moving from one object to another through friction.
When Benjamin Franklin was studying the electrostatic phenomenon, he realized that a lightning rod could prevent lightning from hitting houses/buildings. The lightning rod consists of a metal wire and a piece of metal that directs electricity from the structure to the ground.
Charles Coulomb conducted precise experiments to find out the exact equation for the electrostatic phenomenon. To apply numbers to this equation, a charge of the first and second objects plus the distance between the two objects was needed.