Write a good paragraph or two in your own words about how a motor works. In your account you should include the power supply, brushes (contacts), armature (which is the spinning loop of wire), conventional current, magnetic forces on the current, and how the magnets are arranged.
You may use this Google Form, DC Motors, to submit your paragraph if you wish. Welcome to our online version of Physics II! It will be an adventure, for sure. I decided to begin where I had hoped to pick up after Spring Break--namely, with motors. I am sorry that we can't build them, but we can at least figure out how they work, especially since motors are all around us. So that's what we are going to try to do. Here is what we would have built: We would take some copper wire coated with enamel for insulation, and wrap it around and around a piece of cork on an axle. Then we would take a match and burn off the enamel from the two ends of our piece of copper wire. That's the bare wire shown above. The other end would be on the other side of the axle. The windings of copper wire are called the "armature" of the motor. We would put screws into each end of the axle in order to support the axle on a small frame that is not shown. Then we would take two strips of metal (brass) and nail them to the frame, and then connect each brass strip to one of the two terminals on our power supply, one strip to the positive terminal and one to the negative. When the two bare ends of the armature simultaneously touch the brass strips, we will have a complete circuit and current will surge through the armature. If we have two magnets, one with its North pole facing the armature and the other its South pole, then the sides of the armature will feel a magnetic force according to F = il x B. The two sides of the armature will experience forces, one side an upward force and the other a downward force. That will cause the armature to spin, which, of course, breaks the circuit. But inertia keeps the armature spinning until contact is again achieved when the armature has spun 180˚. The current is established again, and the wires experience a force again, repeating the process. Do you get it? The right-hand-rule will help you figure out how the forces on the sides of the armature are upward on one side and downward on the other. The resources listed in today's assignment will help you figure out what's going on, too. Let's see how it goes, and let me know via email if there are questions or problems. All the best to you all! Assignment:
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Physics II
Mr. Swackhamer Scottsdale Preparatory Academy Archives
March 2020
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