Unit13Concepts

# Unit13Concepts - generator-like behavior by producing an...

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My Blackboard All Blackboard Sites Home Help Logout Course Map Announcements Course Info/Calendar Unit 10 Unit 11 Unit 12 Unit 13 Unit 14 Unit 15 Unit 16 Unit 17 Unit 18 all videos My Grades Unit 13. Time-Dependent Currents. Major Concepts Electromagnetic induction Electromagnetic induction is the phenomena in which an emf is induced in a coil of wire by a change in the magnetic Fux that passes through the coil. A motional emf Separated charges on the ends of a moving conductor give rise to an induced emf, called a motional emf , because it originates from the motion of the conductor. The magnetic Fux The Fux is proportional to the number of magnetic ±eld lines that pass through a surface. Lenz's Law The polarity of an induced emf is such that the induced current produces an induced magnetic ±eld that opposes the change in Fux causing the emf. A back emf When an electric motor is running, it exhibits
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Unformatted text preview: generator-like behavior by producing an induced emf, called a back emf or counter emf . Mutual induction Mutual induction is the effect in which a changing current in a primary coil induces an emf in a secondary coil. Self-induction Self-induction is the effect in which a change in current in a coil induces an emf in the same coil. A transfomer A transfomer is a device for increasing or decreasing an ac voltage. Transfomer property A transfomer that steps up the voltage simultaneously steps down the current, and a transformer that steps down the voltage steps up the current. The capacitive reactance V rms = I rms *X C The capacitive reactance - X C is measured in ohms and determines how much rms-current exist in a capacitor in response to a given rms-voltage across the capacitor. 1 of 1 5/16/09 12:51 PM...
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