Sample Ohm in the Circuit (grades 3-4) Worksheet
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Ohm in the Circuit
By Trista L. Pollard 		  
1     Although Benjamin Franklin had his moment in the "spot light", there were many scientists in the 18th and 19th centuries who worked to discover the mystery of electricity. Franklin's creation of the lightning rod in 1752 sparked the interest of scientists throughout Europe and America. During the late 1700s and 1800s these scientists tried to figure out how to produce electrical energy and how to store large amounts of electricity. This whole "electricity era" started with hanging frog legs, but it ended with an important law for measuring the flow of electricity.
 
2     In 1786, an Italian scientist named Luigi Galvani tried to discover if lightning was truly the key to producing electricity. Prior to an approaching thunderstorm, he took the legs of a dead frog, attached them to a metal hook, and hung the hook from a metal railing. Galvani wanted to see if the lightning would produce an electrical current that would make the legs jump. However, before the lightning could arrive, the legs jumped. After Galvani observed this phenomena, he realized the frog's nerves had made a new type of electricity called animal electricity. People throughout Europe began to believe animal electricity was the secret to life. Now you know why Frankenstein had such a jolt when he woke up. Today the word galvanic stands for the direct current of electricity that is produced chemically. Galvanize means to shock with an electric current. I guess Galvani "galvanized" his frog's legs.
 
3     In the 1790s, another scientist named Alessandro Volta proved that Galvani's animal electricity was really a chemical reaction. A chemical reaction occurs when two or more substances are combined and a new substance is produced. The metal railing on Galvani's balcony reacted to the metal hook that held the frog's legs and the moisture in the air. The result was a mild electrical current that caused the legs to jump. Volta used this knowledge to produce the first battery in 1800. He built the battery by using alternate layers of copper and zinc in a jar of salt water. The chemical reaction that occurred between the two metals and the salt water caused a steady flow of electricity. Volta's work provided us today with the words volt and voltage. Volts are units of potential difference similar to the pressure in the circuit. Voltage is the type of pressure that pushes an electrical charge through a circuit. In addition to new science vocabulary words, Galvani and Volta's work helped other scientists as they learned about circuits and current electricity. Current electricity is the electrical energy that flows through an unbroken path or circuit.

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