nagle_phys2020_fa07_lecture31 - Finish reading Chapter...

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1 73 • Finish reading Chapter 21 (sections 21.1-21.8) • Start reading Chapter 22 (sections 22.1-22.7) • CAPA #11 due on Friday • Note that Exam #3 is on Tuesday Nov. 27 at 7:30 pm just after Thanksgiving break! 74 Why do we use AC Voltage in the United States and most of the world? 1. One reason is the ease of generating from a power generator. Recall a rotating coil in a magnetic field creates an induced current, but it is sinusoidally alternating. (First large scale test at Niagara Falls) 2. AC turns out to be easy to change from one peak Voltage level to another. This is using a Transformer . 75 Transformer – device for transforming AC Voltage from one value (say 120 VAC) to another value (like 10 VAC or 2000 VAC). Made of 2 coils of wire, usually wrapped around an iron core (to help contain the B- field lines). There are no moving parts ! Primary coil = input with N p turns Secondary coil = output with N s turns 76 Transformers work because of Faraday’s Law. t B Δ ΔΦ = ε If there is alternating current going through the primary coil, the magnetic flux going through the coil itself is changing. t N V B p p Δ ΔΦ = | | If the iron core keeps all the field lines inside, then the identical magnetic flux must also go through the secondary coils.
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This note was uploaded on 02/27/2008 for the course PHYS 2020 taught by Professor Dubson during the Fall '06 term at Colorado.

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nagle_phys2020_fa07_lecture31 - Finish reading Chapter...

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