Name: ____________________________________ Benjamin Franklin's Inventions, Discoveries, and Improvements Bifocals A modern replica pair of the type of split bifocal spectacles known to have been worn by Benjamin Franklin in the mid 1780s Bifocals are eyeglasses with an upper and lower half, the upper for distance, and the lower for reading. Bifocals are commonly prescribed to people with presbyopia, a condition that Franklin suffered. Franklin wrote, in August 1784 to his friend George Whatley, that he was "happy in the invention of double spectacles, which serving for distant objects as well as near ones, make my eyes as useful to me as ever they were." Electricity Franklin did not, of course, invent electricity, but he discovered many things about it, previously not understood. Franklin's Kite Experiment Before Franklin started his scientific experimentation, it was thought that electricity consisted of two opposing forces. Franklin showed that electricity consisted of a "common element" which he named "electric fire." Further, electricity was "fluid" like a liquid. It passed from one body to another — however it was never destroyed. In a letter to Peter Collinson, Franklin wrote that the "fire only circulates. Hence have arisen some new items among us. We say B (and other Bodies alike circumstanced) are electricisedpositively; A negatively; Or rather B is electricised plus and A minus ...These terms we may use till philosophers give us better." Franklin's work became the basis for the single fluid theory. When something is being charged, such as a car battery, electricity flows from a positive body, that with an Name: ____________________________________ excess charge, to a negative body, that with negative charge. Indeed, a car battery has plus and minus signs on its terminals. Franklin wrote Collinson in another letter that: "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 posit 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 conductor positively charge plus negatively condensor minus armature They are still the terms we use today. Lightning Rod Rod believed to be an original of Franklin's Once Franklin had an understanding of the behavior of electricity, he set about to protect houses from the destructive forces of lightning. A lightning rod, simply, is a rod attached to the top of a building, connected to the ground through a wire. The electric charge from lightning strikes the rod and the charge is conducted harmlessly into the ground. This protects houses from burning down and people from electrocution. Franklin Stove Franklin's original design for the Franklin stove. In colonial America, homes were warmed by a fireplace. The Franklin stove, invented in 1742, is a metal-lined fireplace that stands in the middle of a room. It has rear baffles for improved airflow. It provides more heat and less smoke than an open fireplace and uses less wood. This cast-iron furnace would Name: ____________________________________ radiate heat from the middle of the room in all directions, and the iron walls even absorbed heat, providing warmth o the room long after the fire went out. Swim Fins Benjamin Franklin was an avid swimmer from a very young age. Throughout his life he consistently promoted its healthful benefits. At the ripe old age of 11 he invented a pair of swim fins. However, unlike today's foot flippers, these were attached to one's hands. His advocacy for swimming was recognized by his induction into the International Swimming Hall of Fame in 1968. Odometer Franklin was curious as to how far he was traveling by carriage, in his role as postmaster, for his travels between Philadelphia and Boston. While the concept of the odometer dates back to ancient times, Franklin did create his own version. The concept was to attach the device near the wheels of a carriage, determine the circumference of the wheel and the number of revolutions required to travel a mile, and have the device register the distance traveled. Name: ____________________________________ Benjamin Franklin, His Inventions, Study Guide Practice Quiz 1. Ben Franklin created Bifocals, and bifocals are commonly prescribed to people with what eye condition? a. Blindness b. Astigmatism c. Presbyopia 2. Bifocals are used to see in which two ways? a. Distant objects as well as near objects b. Distant objects and double vision c. Near objects and Peripherals 3. What does the prefix bi mean? a. Three b. One c. Two 4. What did Franklin name the “common element” in electricity? a. Electric fire b. Electric energy c. Electric movement 5. Electricity has what two types of charges? a. Negative and Negative b. Positive and Neutral c. Positive and Negative 6. What were three electrical terms we gained from Franklin? a. Battery, conductor, condenser b. Fluid, fire, neutral c. Engine, caliper, ignite Name: ____________________________________ 7. What was the purpose of a lightening rod? a. Gather electricity into energy and power houses b. Protect house from burning down and electrocuting people c. Create fires for heating houses and ovens 8. What was the significance of the Franklin Stove? a. It provided more heat and less smoke. b. It provided a larger surface for cooking. c. It could be used by gathering electricity. 9. Where were the Franklin Stoves located in room? a. By the bathroom b. In the kitchen c. In the middle of the room 10. Since Franklin was an avid swimmer, he invented swim fins that were attached where? a. A swimmer’s thighs b. A swimmer’s hands c. A swimmer’s feet 11. Did Franklin make the first odometer? a. Yes b. No 12. How did Franklin’s odometer work? a. It registered speed by using knots tied to a rope and calculating latitude and longitude. b. It tracked speed by a clock device connected to a horse’s leg that counted its steps until reaching a mile. c. It tracked the circumference of the wheel and the number of revolutions required to travel a mile. .