Passage 1
Franklin's Lightning Experiment
by Dave Wurth
In the eighteenth century, people's beliefs in the causes behind natural occurrences were often based on superstition and folklore rather than science. Mysterious and powerful occurrences like lightning were often thought of as a sign of God's wrath. It wasn't until enlightened thinkers began to examine the natural world with objectivity and reason that things changed.
In addition to his contributions as a statesmen and diplomat, Benjamin Franklin was a scientist. Through his experiments, Franklin was able to prove that lightning was a form of electricity. His discoveries revolutionized the field of electrical science and paved the way for later scientists to further unravel the mysteries of electricity.
Electricity was known in the eighteenth century, but only as static electricity. Other forms had not yet been discovered. Discussion grew in scientific circles in France and England, and scientists were slowly making advances in electrical science. Franklin was curious and began experimenting with static electricity.
When Franklin's friend in London, Peter Collinson, sent him a glass rod, Franklin began conducting experiments to generate static electricity. Although Franklin was still a scientific novice, he made some important observations. Franklin saw how, when the glass rod was rubbed with a piece of cloth, it generated a static electrical charge. Franklin wondered if the lightning generated in the sky was also made of the electricity.
Franklin proved his theory during his famous kite experiment in 1752, when he was able to capture an electrical charge from lightning using a kite and a key. Others had conducted similar experiments, but those scientists were impetuous and met with disastrous results. They used conductor rods, and electrical charges from the lightning were conducted from the rod through the human body, causing fatal or near-fatal consequences.
Franklin solved this problem by using a kite instead of a conductor rod. By using a kite, key, and a device called a Leyden jar, he was able to divert the electric charge away from his body. He tied a key to the end of a silk string and tied it to the kite. From the key, he attached a metal wire that went into the Leyden jar. The jar became an early prototype for a capacitor, which is a device used to collect electrical charges. He then attached a silk string from the key.
During a lightning storm, Franklin went outside with his device. Electricity was attracted to the kite, and a charge traveled down the kite string, through the key, and into the jar. Lightning did not directly strike the kite, however; if that had happened, Franklin would have probably been severely or mortally injured.
When Franklin touched the key, he did feel an electric charge. As he suspected, the electrical charges in the sky had negatively charged the key and the Leyden jar, which proved his theory that static electricity is composed of the same electricity generated in the sky.
Because he wanted his experiments to be put toward practical uses, Franklin also invented the lightning rod. A lightning rod is a device meant to save a home or structure from catching fire when struck by lightning. During Franklin's time, this was a common cause of building destruction. The lightning rod extends into the sky above the height of the building to attract lightning. Attached to the rod is a metal cable that conducts the electrical charge down the side of the building and safely into the ground.
Franklin's invention of the lightning rod is considered one the most important accomplishments of his life. After 200 years, his design remains the same and is used in buildings around the world. Many of Franklin's contributions to electrical science are still relevant—and terms he invented, such as "charge," "discharge," "condenser," "conductor," "battery," and "electric shock," are part of standard electrical jargon to this day.
Passage 2
Franklin's Lightning Rod
by Scott Thomas
Lightning was the cause of many fires in the eighteenth and nineteenth centuries. Many homes and other edifices were built using flammable materials such as wood. Homes could easily catch fire when lightning struck. With the passing of one fierce storm, people could potentially watch their entire livelihood go up in flames.
Benjamin Franklin was the Prometheus of his time. He was a tireless initiator of social progress. When he saw something that the public needed, he set about addressing it. He helped launch Philadelphia's first police force, first volunteer fire company, first fire insurance firm, and other public institutions. He was diligent about public safety.
When Franklin finally proved that lightning was made of electricity, it impelled him to think about conductors. Conductors, he reasoned, could be used to protect people, buildings, and other structures from lightning. This led to his development of the lightning rod.
The lightning rod Franklin developed was made of iron and had a pointed tip. It was about 8 to 10 feet long. Franklin theorized that ". . . the electrical fire would, I think, be drawn out of a cloud silently, before it could come nigh [near] enough to strike. . ." Two years before his famous kite experiment, Franklin had already seen that a sharp iron needle would conduct electricity away from a charged area.
If the rod were affixed to the top of a structure, he argued, the tip could collect the electric charges from the atmosphere. From there, the rod would connect to another conductor that ran the length of the structure. The electric charge would then be drawn down the pointed rod and through the conductor. Electricity would then have a safe path to travel away from the structure to the ground. "Would not these pointed rods. . . ." Franklin wrote, "secure us from that most sudden and terrible mischief?"
Franklin tirelessly advocated his lightning rod. When King George III had one installed on his palace, the American colonies quickly followed suit. Soon, lightning rods were found on the tops of churches, homes, and other buildings across early America.
Not all lightning rods were used on land. Ships were also vulnerable to lightning strikes while at sea. Wooden ships could easily be set ablaze by lightning during tumultuous storms. Slowly, over time, lightning rods were found on ships as well.
As one ship captain wrote to Franklin, "Notwithstanding the pains several eminent Philosophers have taken, to bring Conductors into general use . . . 'tis too true that very few Vessells are furnished with them, tho' scarce a year passes that does not afford us Instances . . . of Ships being struck by Lightning."
15
Which evidence from "Franklin's Lightning Rod" best supports the claim that the lightning rod was a success?
A.
"If the rod were affixed to the top of a structure, he argued, the tip could collect the electric charges from the atmosphere."
B.
"Electricity would then have a safe path to travel away from the structure to the ground."
C.
"Soon, lightning rods were found on the tops of churches, homes, and other buildings across early America."
D.
"Many homes and other edifices were built using flammable materials such as wood."