We reviewed a few things about current, potential, voltage, and power today. It's important to have clear ideas about what we mean by "current" and "potential." One of the more useful ideas in understanding electric circuits is that two points connected directly by copper wire in a normal electric circuit will have the same potential, for all practical purposes. Another observation we made that makes sense is that the amount of current entering a circuit element is the same as the amount of current leaving that element. Of course, the current loses some of its associated potential energy, resulting in some change in the circuit element. For example, light bulbs light, diodes light up, too, and resistors get warm. So some of the energy carried to the element by the current is lost to the environment, and less energy therefore is carried by the current as it leaves the element. We also dealt a bit more about wiring in our houses. Three wires from the electric utility enter our homes, two 120 Vrms "hot" wires (out of phase with each other) and one neutral wire. We also have a ground for our homes, a metallic attachment to Earth. A few of the appliances in our houses require 240 V. We saw how the two hot wires can be hooked up to enable that. And the outlets and plugs. Finally, we saw how circuit breakers work. Assignment:
We began to learn a few basics about the wiring in our houses today. In addition, we made glass conduct electricity. Like silicon diodes, glass, which is made up of silicon dioxide with sodium and calcium ions within, conducts when it gets soft as it is heated; the ions can begin to drift and thereby produce a current. Here is what we did: There seemed to be little difficulty with these Power in Electric Circuits as we calculated the energy used in electric circuits and the cost one would pay to the electric utility.
We presented our solutions to Ch 20 P: 1 - 9. It all went smoothly. I hope that indicates good understanding. I am usually more comfortable with more questions and difficulties, but maybe everything is good!
Assignment:
Students worked on Basic Circuits consisting of one, two, and three light bulbs. Currents and potentials were measured. Work was finished by Thursday.
Assignment:
Here are a few more conceptual questions that deal with Chapters 16 and 17, although not much specifically related to the electric fields and potentials created by charged particles.
Here's the equation sheet that you will receive for the Semester Exam. We revisited some of our past material today in preparation for the Semester 1 Final Examination. The Exam will consist of about 50 multiple choice items and a handful of problems to solve. Count on roughly 75 minutes to complete this exam, assuming we work about as fast as students in past years.
Linked below are some things that you should be able to handle: Assignment:
Does a metal cloak really provide complete shielding? I dunno. Check this out to see the answer: We navigated our way through Ch 16 P: 23, 24, 25, and 27 successfully.
Next up were equipotential lines, a way to represent an electric field. |
Physics II
Mr. Swackhamer Scottsdale Preparatory Academy Archives
March 2020
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