Download - Magnetic Induction
![Page 1: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/1.jpg)
Magnetic Induction
Transforming energy with magnetism
![Page 2: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/2.jpg)
Lorentz Force Reminder
F = qv B
Source: Griffith, The Physics of Everyday Phenomena
F is directed out of the screen.
![Page 3: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/3.jpg)
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.
![Page 4: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/4.jpg)
–
Moving Creates a Potential
v
B
induced potential+
![Page 5: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/5.jpg)
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
![Page 6: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/6.jpg)
Rotating Loop Creates Circuit
B
V
V
![Page 7: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/7.jpg)
Rotating Loop Creates Circuit
B
V V
![Page 8: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/8.jpg)
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
![Page 9: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/9.jpg)
Group Work
c. What is the current direction at these points?
a b c d e
![Page 10: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/10.jpg)
Faraday’s Law
• Greatest flux when perpendicular • Fastest change in flux /t when parallel
a b c d e
![Page 11: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/11.jpg)
Rotation Powers a Generator
v
v
Motion
VVinduces a potential
which generates a
currentthat charges the
battery
B
through the field
![Page 12: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/12.jpg)
Lenz’s Law Explains Generator
B
changing field
opposing field
needed I
![Page 13: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/13.jpg)
Current in a Field Feels a Force
F
B
I
![Page 14: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/14.jpg)
Loop in a Field Has Torque
B
I I
![Page 15: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/15.jpg)
Torque Turns a Motor
I
I
current I
force F
B
![Page 16: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/16.jpg)
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?
![Page 17: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/17.jpg)
How a Microphone Works
microphone
geophone
Flux inside loop becomes more
![Page 18: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/18.jpg)
How a Loudspeaker Works
loudspeakerinduced motion of magnet
currentcurrent-generated field attracts or repels magnet
![Page 19: Magnetic Induction](https://reader035.vdocuments.us/reader035/viewer/2022081421/568158ec550346895dc62cda/html5/thumbnails/19.jpg)
Back Potential
• As the motor turns, back-potential B/t opposes
• Faster rotation more back potential
I
B