The “Electric Kiss”

On the next cold, dry night, do a quick shuffle across the carpet in your shoes and ask your mom for a kiss. Guaranteed she'll jump with excitement—not because you actually kissed her (that hasn't happened since you were eight, or was it nine?) but because your kiss will have “zapped” her with a mild jolt of electricity. Sound like fun? Well . . . for you, anyway! In fact, did you know that centuries ago, an “electric kiss” between two people, one of whom was charged with electricity, was a form of romantic amusement?

We commonly think the study of electricity began in 1752, when Ben Franklin flew a special kite into a thundercloud (see “Smart Ben,” page 14). But actually, the Greek philosopher Thales, who lived nearly 27 centuries ago, was probably the first person to experiment with electricity—static electricity. Thales found that if he vigorously rubbed amber (fossilized tree sap) with a cloth, the amber would suddenly possess the power to attract lightweight objects like feathers, leaves, and bits of paper.

What caused this seemingly magical attraction? In the mid-1500s the Italian mathematician and astrologer Girolamo Cardano suggested that, since amber contains a “sticky” fluid, lightweight objects (like feathers) must be attracted to amber because they have a “desire to absorb” its fluid. Although Cardano missed the boat on that one, the effect nevertheless became named after elektron, the Greek word for amber; these objects were then “amberized” or “electrified.” (The term “static electricity” came into use much later when the phenomenon was better understood.)

The first machine designed to “electrify” objects appeared in the mid-1600s. The device was simply a sulfur ball, about the size of a child's head, that spun on an axle mounted horizontally in a wooden frame. The contraption looked sort of like a spinning wheel plump with thread. To become “electrified,” all you had to do was place your dry hands against the rapidly rotating sulfur ball and voil?!… “How about a kiss, dear? …ZAP!”

The sulfur ball was replaced in 1709 with a glass globe. Soon these electric machines took on some wonderfully intricate designs. In fact, three years before his kite experiment, Ben Franklin had one of these machines built for him. Actually, lots of “electrifying” discoveries had happened before then. Experimenters had discovered that many materials other than amber could be “electrified” (including a shoe rubbed against a fur coat). On the other hand, they also learned that not all objects became electrified. Furthermore, objects “electrified” by the same machine appeared to repel each other (like magnets of the same charge); and objects “electrified” in different ways (one by touching an electric machine, for example, and the other, say, by rubbing amber) would attract each other (like magnets of opposite charge).

These discoveries led to some fantastic experiments, many of which were used for fun and entertainment. Some experimenters designed ways to perform what can only be considered “magic tricks.” Consider the illustration on pages 12–13: A boy, lifted horizontally off the ground by silk ropes, places his feet against the rotating glass ball of an electric machine and becomes “electrified.” He touches the left hand of a woman and “electrifies” her. The woman holds her right hand over a table covered with pieces of paper. Since the woman's hand is now “electrified,” the paper will be attracted to her hand and lift off the table?like magic! Note that the woman stands on a barrel of hardened wax, which is a substance, like the silk ropes holding the boy, that canswert be “electrified.”

In 1745, two scientists independently discovered a way to trap or store what was believed to be the “electric fluid” produced by these machines. And what better way was there to collect electric fluid than in a glass container? This particular jar, called a Leyden jar after the Dutch city where it was developed, was filled with water and sealed with a rubber stopper that had a wire through it. The idea was to “pour” electric fluid into the water by touching the external part of the wire to the spinning globe of an electric machine. Indeed, such experiments worked, and the experimenters received a powerful shock when they placed their moist hands on the jar as they went to remove it from the machine.

Perhaps you guessed it? Yes, once the experimenters learned how to control the electric jolt produced by the Leyden jar, people began lining up to receive the painful shocks from this new device. It was the rage of the times! One ambitious experimenter placed a series of these jars in such a way that their power was added together. He then lined up 700 volunteers, all of whom were connected by short wires. When the wires from the two people at the ends of the line were connected to the battery of Leyden jars, all of the 700 people became shocked and suddenly sprang simultaneously into the air.

But the enticing, playful power of electricity was soon learned to have its limitations. When Ben Franklin performed his kite experiment, he did not know if it would be his last. Indeed, Franklin was lucky. A year later a Russian scientist, Georg Richmann, was killed by ball lightning (see “Mystery Lights, page 28) while conducting an experiment similar to Franklin's. For Richmann, playing with electric fire turned out to be the “kiss of death.”

Editor's Note: We've had some fun in this article describing early experiments with electricity. Keep in mind that the experimenters were unaware of the serious dangers involved.

CAUTION: Don't attempt any electrical experiments (except the static electricity kiss) unless you are supervised by an adult. Water and electricity combined can be fatal.

Vocabulary

intricate:
Complicated; complex.
Leyden jar:
An early electric circuit consisting of a glass jar lined inside and out with tinfoil, and having a conducting rod connected to the inner foil lining and passing out of the jar through an insulated stopper.
sulfur:
A pale yellow nonmetallic element.
static electricity:
An electric charge that builds up on a material.

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Activity

  1. This article mentions a boy who becomes “electrified” after touching his feet to a rotating glass ball. Then he touches a woman's hand, and she becomes “electrified.” She then places her hand over a table covered with pieces of paper, and one of the papers lifts off the table toward her hand. Describe how an electric charge is passed from the glass ball to the woman's hand. Describe why the papers are attracted to the woman's hand.
    Answer: When the boy touches his feet to the spinning glass ball, he changes his charge from neutral to positive. He passes this positive charge along to the woman by touching her hand. The neutrally charged papers on the table are attracted to the positive charge of her hand.
  2. What might happen if the boy touched the ball and then tried to pick up a piece of paper that had also been touched to the ball? Why?
    Answer: The boy's hand would repel the paper because both the boy and the paper would have the same electric charge. When two things have the same electric charge, they repel each other.
  3. What was a Leyden jar designed to do?
    Answer: A Leyden jar was designed to trap what people thought was electrical fluid.
  4. Why would it be dangerous to touch a Leyden jar with moist hands after the jar had been connected to an electric machine? Would it be less dangerous to touch the jar with dry hands? Why?
    Answer: It would be dangerous to touched an “electrified” Leyden jar with wet hands because a person would receive a powerful shock of electricity. Touching the jar with dry hands might be safer because there would be no water to pass along the electric charge from the glass to the hands.

Activity

  1. This article mentions a boy who becomes “electrified” after touching his feet to a rotating glass ball. Then he touches a woman's hand, and she becomes “electrified.” She then places her hand over a table covered with pieces of paper, and one of the papers lifts off the table toward her hand. Describe how an electric charge is passed from the glass ball to the woman's hand. Describe why the papers are attracted to the woman's hand.
    Answer: When the boy touches his feet to the spinning glass ball, he changes his charge from neutral to positive. He passes this positive charge along to the woman by touching her hand. The neutrally charged papers on the table are attracted to the positive charge of her hand.
  2. What might happen if the boy touched the ball and then tried to pick up a piece of paper that had also been touched to the ball? Why?
    Answer: The boy's hand would repel the paper because both the boy and the paper would have the same electric charge. When two things have the same electric charge, they repel each other.
  3. What was a Leyden jar designed to do?
    Answer: A Leyden jar was designed to trap what people thought was electrical fluid.
  4. Why would it be dangerous to touch a Leyden jar with moist hands after the jar had been connected to an electric machine? Would it be less dangerous to touch the jar with dry hands? Why?
    Answer: It would be dangerous to touched an “electrified” Leyden jar with wet hands because a person would receive a powerful shock of electricity. Touching the jar with dry hands might be safer because there would be no water to pass along the electric charge from the glass to the hands.