04_23_Induction_Review

# 04_23_Induction_Review - Faraday’s & Lenz’z Law E =...

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Today4/23 o Magnetic Induction Review o HW Questions? o Exam 4/24 o Force and motion of charged particles o B-fields due to wires o Force and Torque on current loops o Forces from currents (like 4/16 Wires 2) o Induced current (like 4/17)

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Magnetic Induction o The current only flows while: o the B-field is changing o the ring is moving o the magnet is moving o It’s all about a “changing” B field!!! o Look at whether the # of field lines are increasing or decreasing
Force on Current Loops o Ch 21: Force/Torque arises from a battery operated loop in a static B-field. o Ch 22: Current in loops “induced” by a “changing” external field. The loop then reacts as in Ch 21. o In fact, battery operated loops resist the changing field caused by themselves! Called “Self Induction” see 22.8

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Unformatted text preview: Faraday’s & Lenz’z Law E = - ∆ Φ ∆ t Φ is the # of field lines inside loop Lenz’s Law Loop “Voltage” Φ can change in many ways: changing B-field changing loop area changing loop angle changing B-field angle This is the “equation” you will see on the exam E = - ∆ Φ ∆ t Using o Identify initial field direction o Identify final field direction o Determine direction of the “change” o Use Lenz’s law to determine B-field due to the current induced around the loop o Use RHR #2 to find direction of induced current Energy Considerations o It takes energy to push current around a loop o Therefore, forces arising from induced currents must always serve to retard (or slow down) the object...
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## This note was uploaded on 12/21/2010 for the course PHYS Physics 21 taught by Professor Larrywatson during the Spring '08 term at North Dakota.

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04_23_Induction_Review - Faraday’s & Lenz’z Law E =...

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