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20.6 Force between Two Parallel Wires

Wire #1 has a magnetic field

that produces a force on wire #2

d

IB o 11 2

221

2 2l

d

IIF o

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20.7 Solenoids and Electromagnets

The magnetic field of the coil can be increased by adding an iron core.

l

INB o

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20.9 Torque on a Current LoopTorque = (Force)(Lever Arm) = NIAB

sinθ

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20.10 Applications

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20.11 Mass Spectrometer

Determine a particle’s mass

Discovery of isotopes

E

rBqBm

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20.12 Ferromagnetism

Magnetic domains: groups of aligned atoms

What do they look like?

The motion of electrons in atoms: orbiting and “spinning”

Most objects are non-magnetic since the electron motions are cancelled out by other electrons

Magnetic permeability B = Bo + BM

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Determine the direction of the force on a positive charge.

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Determine the direction of the velocity on a negative charge.

F

F

F

F