Download 4.3.1

The Earth’s Shield
4.3.1 Magnetic Fields and
Electromagnetic Induction
Electromagnetic Induction
• All charges produce ELECTRIC FIELDS
• Moving charges produce MAGNETIC FIELDS
– PERPENDICULAR to the motion of the charge
Magnetic field lines
Making a Magnet
• Magnetism is a FIELD FORCE
• No contact required
• All atoms have “some” natural of magnetism
• Three strongly magnetic elements
• IRON, NICKEL, COBALT
Electromagnetic Induction
• Magnets produce magnetic fields
• Moving magnets produce ELECTRIC FIELDS
– PERPENDICULAR to motion of the magnet
– This causes ELECTRICAL CURRENT to flow
Magnetic Field Lines
• Rules for field line directions
• Outside magnet  NORTH TO SOUTH
• Inside magnet  SOUTH TO NORTH
Magnetic Field Maps
N
S
N
S
Magnetic Field Maps
S
N
N
S
Magnetic Field Maps
S
N
Example #1
• Determine the direction of the magnetic field lines at
each point. Where is the field strongest?
Field is strongest
at point C.
A
B
N
S
C
D
Example #2
• Determine the direction of the magnetic field lines at
each point. Where is the field strongest?
H
E
S
N
N
F
Field is strongest
at point F.
G
S
Compass
• The needle of a compass is a small MAGNET
• The north pole of a compass needle
– … is marked with a small “N” or a prominent color
– … points toward magnetic SOUTH poles.
Example #3
• Determine the direction in which the compass will
point.
S
N
S
N
Earth’s Magnetic Field
The
Convection
geographic
NORTH
currents
pole
inof
the
the
Earth
outeracts
ironlike
core
the
SOUTH
produce
polethe
of a
Earth’s
magnet!
magnetic
field
The Magnetosphere
End of 4.3.1 – PRACTICE