Notes on Chapter 30

# Notes on Chapter 30 - Chapter 30 Induction and Inductance...

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1 July 2010 1 - Chapter 30 - Induction and Inductance Current Magnetic Field Faraday suggested the possibility of obtaining an electric field from magnetic field which will, in turn, give a current: Magnetic Field Electric Field Current Faraday’s law of induction 30 - 1 What is Physics?

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1 July 2010 2 Two Experimental Observations (1) Experiment 1 Current flows only when there is relative motion between the loop and the magnet; the current disappears when the relative motion ceases Faster motion produces a greater current If moving N pole toward the loop causes a clockwise current, then moving a S pole toward the loop causes a counterclockwise current The current produced in the loop is called an induced current The work done per unit charge to produce the current is called an induced emf The process of producing the current and emf is called induction 30 - 2
1 July 2010 3 (2) Experiment 2 Observations : When switch S is closed, the meter suddenly and briefly registers an induced current Then, if the switch S is opened, another sudden and brief induced current appears but in the opposite direction There is no induced current when the current in the right loop is constant We need to identify the quantity that is changing and thus causing the induced emf and induced current

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1 July 2010 4 Faraday’s Law of Induction Qualitative statement Faraday realized that an emf is induced in the loops at the left (previous figures) when the number of magnetic field lines that pass through the loop is changing Note that the emf is obtained without the use of a battery 30 - 3
1 July 2010 5 SI unit of magnetic flux is the weber 1 weber = 1 Wb = 1 T.m 2 Quantitative Treatment Define magnetic flux Φ B cos B d B dA B dA BdA φ Φ= = = cos B B dA BdA = ∫∫ cos B BA Over a flat area A the magnetic flux is: B ˆ n A Ф A

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1 July 2010 6 The magnitude of the emf E induced in a conducting
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Notes on Chapter 30 - Chapter 30 Induction and Inductance...

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