Electromagnetism Question 1 What influences the strength of an electromagnet? What property does a needle inside a compass possess? Magnet Since a magnet repels and attracts it. What affect does increased current have on an electromagnetism? Increased current increases electromagnet strength Added more batteries and the needle moved more. 5/14/02 8:57 AM What effect does the number of coils have on electromagnetism? More wraps made the magnetic stronger since the needle moved more. How else can you increase the "induced" magnetism? Induce magnetism Put current in a wire. To increase Greater current More wraps in the wire ( coil) Add iron core to concentrate the magnetism Mar 20 9:37 AM 1
Electromagnetism Question 2 Just what is magnetism? Discuss how what you observed with the circuit and compass relates to the water waves model the author presented. Boat has a wake boat is the current in the wire wire. The wake was the magnetic field around the 5/14/02 9:06 AM Electromagnetism Question 3 What factors influence production of electricity by magnets? How d oes the direction you move a magnet influence the electricity produced? Induced electricity by moving a magnet in a coil of wire. Had to move fast enough. The direction of the magnet the LED light either on the way in or way out because the you were reversing the flow of current. Reverse the magnet, the LED light the opposite way because the opposite poles affected the direction of current flow. How is an LED different from a regular light bulb? LED is a one way bulb and will only light when the current is flowing the correct direction. A regular bulb lights either way. 5/14/02 9:08 AM 2
How does the speed which you move a magnet influence the electricity produced? The faster you move the magnet, you get more current because you have more voltage. What do the + and signs tell you? They indicate the direction of current flow or voltage, + or on the meter. 5/14/02 9:09 AM Electromagnetism Question 5 What is mutual induction? What was necessary for one coil to produce current in the secondary? The coils had to be close to each other so the magnetic field can influence the second coil. What factors effected the amount of current "induced"? Enhanced by adding more current in the first coil, added iron core ( bolt), not tested but if you wrap the second coil with more turns of the wire, the effect increases. 5/14/02 9:11 AM 3
How does the author's surfing model relate to your observations? The wire has a current which creates a magnetic field ( wake) that causes a nearby wire to get a current ( surfers) Current in first induced magnetic field which induces current in the second. 5/14/02 9:12 AM Capacitance Question 1 What factors influence capacitance? If you were adding negatives to the water inside the film canister, what type of charge was accumulating on the aluminum outside? Positives but we did it the opposite way. So for us, the can inside was positive and the foil became negative. What was the source of this charge? The positive on the outside would have happened when electrons left in through your hand from the ground. We did it the opposite meaning the negatives come in from the ground. Why would larger conductors have a larger capacity? Large would give a bigger shock. Ben Franklin shocked turkeys for dinner. What role does the plastic container have in the capacitor? Plastic is an insulator. 5/14/02 9:13 AM 4
Capacitance Question 2 How do you explain capacitance? How would the author express the above questions? Party in parking lot, a wall separates the guys and girls. The wall is the insulator. 5/14/02 9:15 AM Describe a model for capacitors that would be appropriate for middle school students. 5/14/02 9:17 AM 5
Using the Wizard is an interesting method for the author to introduce a review of the topics discussed. Briefly, what are the key concepts of electricity developed in the story up to this point? Voltage causes electrons to flow. Current is flow of electrons Resistance is how easy it is for electrons to flow. Resistance is increased by longer wire, thinner wire and materials like nichrome capacitance stores charge, does not create like a battery. REDOX reaction chemical reaction. Unit is farad. AC alternating direction 60 times a second Frequency in Hertz 60 hertz DC direct current one way only. Induction cause current by using a magnet or magnetism by using current. Self induction when current flows, magnetism is induced which induces current that opposes the first current. 5/14/02 9:17 AM May 11 1:41 PM 6
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