Magnetic Induction Transforming energy with magnetism.

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Magnetic Induction Transforming energy with magnetism

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CPS Question B I What is the direction of the Lorentz force on the charges moving in this wire? A. B. C. D. E. F.

Transcript of Magnetic Induction Transforming energy with magnetism.

Page 1: Magnetic Induction Transforming energy with magnetism.

Magnetic Induction

Transforming energy with magnetism

Page 2: Magnetic Induction Transforming energy with magnetism.

Lorentz Force Reminder

F = qv B

Source: Griffith, The Physics of Everyday Phenomena

F is directed out of the screen.

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CPS Question

B

I

What is the direction of the Lorentz force on the charges moving in this wire?

A.

B.

C.

D.

E.

F.

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Moving Creates a Potential

v

B

induced potential+

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Motional emf

• Moving a conductor through a magnetic field causes separation of charges.

• Back-emf (motional emf) in conductor cancels potential from motion

= lvB• when l, v, B all orthogonal

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Rotating Loop Creates Circuit

B

VV

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Rotating Loop Creates Circuit

B

V V

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Group Work

a. At which position(s) does the most magnetic flux pass through the loop?

b. At which position(s) does the magnetic flux through the loop change the fastest?

a b c d e

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Group Work

c. What is the current direction at these points?

a b c d e

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Faraday’s Law

• Greatest flux when perpendicular • Fastest change in flux /t when parallel

a b c d e

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Rotation Powers a Generator

v

v

Motion

V Vinduces a potential

which generates a

currentthat charges the

battery

B

through the field

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Lenz’s Law Explains Generator

B

changing field

opposing field

needed I

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Current in a Field Feels a Force

F

B

I

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Loop in a Field Has Torque

B

I I

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Torque Turns a Motor

I

I

current I

force F

B

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Group Work

If the magnetic field intensifies, in what direction will the induced current be?

B

Which direction is the flux change?

What current would oppose it?

What is the Lorentz force on each side?

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How a Microphone Works

microphonegeophone

Flux inside loop becomes more

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How a Loudspeaker Works

loudspeakerinduced motion of magnet

currentcurrent-generated field attracts or repels magnet

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Back Potential

• As the motor turns, back-potential B/t opposes

• Faster rotation more back potential

I

B