Magnetic Field: General Phenomena

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Magnetic Field General Phenomena
Electric Field (E) Magnetic Field
q, -q
North and south poles
Like/dislike charges repel/attract
Like/dislike poles repel/attract
There is no magnetic monopole north and south
poles ALWAYS come in pairs
Magnetic field Outside a magnet N to S
Inside a magnet S to N
Magnetic field lines always close on themselves
no source or drain.
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General Phenomena Continue

• Magnets only attract certain materials

• Magnetic materials Fe, Co, Ni some rare earths
  Sm. Nd.

• Some magnetic materials can generate magnetic
  field Permanent magnet

2. Action at distance (through field) demo

• only magnetic materials can shield magnetic
  field

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Charges in a magnetic field
Right hand Rule
Concept Check
In which situation does the magnetic field points
to the left?
Answer (A)
(A) (B) (C)
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Magnetic Force on a MOVING charges Continue

• F0 if

• V0

• VB

2. If F?B (or V?B ), what type of motion does a
charge have?
Circular motion accelerator, mass spectrometer

• B field can be used to change the direction of
  a moving charge

• magnetic force cannot do work on a charge.
  Magnetic field cannot change the speed of a
  charge, only E field can

Net EM force on a charge
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Circular Motion General
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Circular Motion Plane ? B
Helical path V?0
Circular path V0