Activities:
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1.How can you make a battery? You will need 12 copper coins and zinc washers close in size. You will also need 12 circles cut out the same size from blotting paper, vinegar, salt, 6 ½ feet of thin plastic coated wire and an iron nail. Pour the vinegar into a glass and put in a tablespoonful of slat. Soak each disc of blotting paper. Stack a coin then a washer then a disc, and finish with a washer. Take the wire and wrap it around the nail as many times as possible. Put one end of the copper wire on top of the copper coin and the other end toward the washer. Bring the nail near a small compass and the needle should spin. The salt and vinegar mixture results in a chemical reaction. Negatively charged particles flow through the coin through the washer around the wire and back to the battery. The current causes a magnetic field that affects the compass. 21
Students may also want to try making a lemon battery. You need a juicy lemon, a copper and zinc nail. Put both nails into the lemon. Touch both nails with your tongue and there should be a tingling feeling as the current flows from the battery.22
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2. How can you make an electromagnet? You will need a large iron nail, a long piece of wire, a battery, and some small paper clips. Wrap the wire around the nail leaving about six to eight inches of wire at each end. Attach the ends to the battery. Try picking up the paper clips with the end of the nail. Students can extend this demonstration by seeing if the power of the magnet is affected if more batteries are added. Also, if more or less wire is wrapped around the nail does the strength of the magnet change? Would you still be able to make an electromagnet if the wire were wrapped around a piece of wood? 23
Students can see that unlike a permanent magnet the poles can be reversed by merely changing the wires hooked up to the battery. This principle is what Oersted discovered and used to develop the electromagnet. Electricity could make a magnet.
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3. Michael Faraday showed the opposite. A magnetic field could produce electricity. How can we make a Magnetic Dynamo? You will need a bar magnet, 5 feet of insulated copper wire, a compass, glass, and 4 twist fasteners like those found on grocery items or garbage bags. Wrap the wire around a drinking glass leaving about 18 inches of wire at each end. Slide the wire off the glass and tie it with the fasteners. Wrap both ends of the coil around the compass in the same direction. Then lift the coil up and pass the bar magnet through it. Moving this magnet back and forth the needle jumps. If you remove the magnet it stops the current flowing. This type of electrical current is called alternating current.24
Once students have made the battery it is a good time to have them experiment with batteries to understand simple circuits, both serial and parallel.
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4. Can you make the bulb light up? For this activity you will need some wire, a bulb and battery. Allow students to work with a partner or on their own to try and light the bulb.
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5. Once you light one bulb give them more. If they attach more what happens to the brightness of the bulbs. In this kind of circuit or series the bulbs will get progressively dimmer. In a parallel circuit, which we find in our homes, and schools, the bulbs are connected so that their number does not affect the brightness of the individual bulbs.
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6. How does a flashlight work? Give students an old flashlight and let them look at the inside and try to trace the circuit that lights up the bulb. Let them see how the switch makes and breaks the connection. After students are familiar with the flashlight and how it works you can see if they can figure out what is wrong when you reverse one of the batteries, put a piece of paper between the two batteries or remove the coil at the ends of the case.25
Background:
Galvani's experiment intrigued Alessandro Volta (1745-1827) who was a professor of physics at Padua University. He believed that the electricity from the experiment came from the metals - the knife and the metal table the frog laid on. A big argument ensued between the two men and each had their followers who claimed the other side was crazy. Both in their way were right. Volta is best known for inventing what is called the voltaic pile, or electric cell. We know it best as a battery.26
Hans Christian Oersted (1777-1851) was the self-educated and through his own hard work he became a professor of physics at the University of Copenhagen. He thought that electricity and magnetism were somehow connected. While lecturing he discovered that the needle of a compass when brought close to his electronic equipment moved. He experimented and found that when the current was on the needle swung one way and when it was shut off the needle swung back. Oersted found that the current was not only deflected by the needle but the magnet. He discovered that a current of electricity creates a magnetic field and thereby connected electricity and magnetism for the first time.27
William Sturgeon (1783-1850) was the first to produce an electromagnet. An electromagnet is a magnet that works by having an electrical current pass around it. Wire is wrapped around a piece of iron and when the electric current goes through the wire it magnetizes the wire. When the current is turned off the magnetic force no longer exists. Sturgeon and his experiments had profound influence on the work of Michael Faraday.28
Michael Faraday (1791-1867) was an English physicist who combined what he learned about electricity and magnetism and developed some of his own ideas which became the foundation for our modern day methods of generating electricity on a large-scale basis. Faraday took Sturgeon's work on electromagnets and tried to see if magnetism could produce electricity. Through his experiments Faraday found that when he started or stopped the electronic current there was slight movement in the galvanometer. He reasoned that the electricity was induced when there was a change in the magnetic force. In other words if the lines of force were constant there was no current. Once the lines of force were created or stopped the electric current was induced. Faraday continued to experiment. He wanted to be able to generate a constant current. He built a device in which a moving magnet induced a current. The amount of current was determined by how fast or slow the magnet changes the field of force. Faraday's experiment proved to be the first electric generator or dynamo. It was the first device to change mechanical energy into steady electric current. Today's electric generators provide energy throughout the world. More electricity is produced by Faraday's discovery than by any other means. There are other ways to produce electricity but all of them put together cannot equal the amount of energy produced by Faraday's generator.29
As often happens at almost the same time as Faraday was working on his theory, Joseph Henry (1797-1878) was working on a theory of induction in America. He was shocked when he read about Faraday's research in a scientific journal. Henry did not give up but kept working. Henry is credited with discovery of the principles of self-induction. This would be a critical step in the later development of the modern generator and electric motor. Henry also discovered the principles of the transformer.30