4.3.1 Magnetic Fields and Electromagnetic Induction

The Earth’s Shield

• All charges produce ELECTRIC FIELDS• Moving charges produce MAGNETIC FIELDS

– PERPENDICULAR to the motion of the charge

Magnetic field lines

Electromagnetic Induction

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

• Magnets produce magnetic fields • Moving magnets produce ELECTRIC FIELDS

– PERPENDICULAR to motion of the magnet– This causes ELECTRICAL CURRENT to flow

Electromagnetic Induction

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

N S

• Determine the direction of the magnetic field lines at each point. Where is the field strongest?

Example #1

Field is strongest at point C.

B

A

C

D

• Determine the direction of the magnetic field lines at each point. Where is the field strongest?

Example #2

Field is strongest at point F.

F

E

G

H

S N N S

• 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.

Compass

• Determine the direction in which the compass will point.

Example #3

S N S N

Convection currents in the outer iron core

produce the Earth’s magnetic

field

The geographic NORTH pole of the Earth acts like the SOUTH pole of a

magnet!

Earth’s Magnetic Field

The Magnetosphere

End of 4.3.1 – PRACTICE