Magnetism

Ferromagnetic Materials–Iron, Nickel, and Cobalt

Magnetic Domains

Magnetic Tape

The Earth’s Whimsical

Magnetic Field

–Magnets have Magnetic Fields.–Moving electrons produce magnetic fields.–Earth's Magnetic Field

Where does the field come from?

The earth’s magnetic field is thought to be generated by fluid motions in the liquid, outer part of the earth’s

core.

Diagram of Movement

• The earth’s core has molten iron and nickel, which are good conductors.

• Buoyancy forces force the fluid to rise.• The fluid cools at the Earth’s outer core.

Earth’s Magnetic Field Direction

The study of paleomagnetism has demonstrated that the Earth's magnetic field has changed over time.

Paleomagnetism refers to the orientation of the Earth's magnetic field as it is preserved in various magnetic iron bearing minerals throughout time.

Magnetic Field and Continental Drift

The magnetic poles are moving by about 10 km per year.

Geomagnetic Polarity Reversals

Example of Ocean FloorMagnetic Anomalies

Decreasing Field Over the YearsEarth's Magnetic Field Trends

52,000.0053,000.0054,000.0055,000.0056,000.0057,000.0058,000.0059,000.0060,000.00

Year

Tota

l Int

ensi

ty (n

T)

The intensity of the magnetic field (inTesla) decreases more rapidly in recent years.

The Magnetosphere

The magnetic field lines generated in the mantle then spread to the surface of the earth and create the magnetosphere which protects the earth from radiation from the sun (solar wind).

The Earth's Magnetosphere1) The solar wind is a stream of ionized gases that blows outward from the Sun at about 400 km/second.

2) The Earth's magnetic field shields it from much of the solar wind. When the solar wind encounters Earth's magnetic field it is deflected.

3) The magnetosphere represents a region of space dominated by the Earth's magnetic field in the sense that it largely prevents the solar wind from entering.

Van Allen Belts

Some high energy charged particles from the solar wind leak into the magnetosphere and are the source of the charged particles trapped in magnetic field lines called the Van Allen belts.

Aurora Borealis & Aurora Australis

When trapped charged particles in the Van Allen Belts react with atmospheric molecules they emit light.

This creates the appearance of luminous bands or streamers called auroras.

Electric Currents and Magnetism.

There is more to it than like poles repel and opposite poles attract. It has to do with electrical

charge.

Oersted’s discovery

Moving electrons create a magnetic field!

X

Field around a current carrying straight conductor

http://www.walter-fendt.de/ph14e/mfwire.htm

solenoid (or inductor)

http://webphysics.davidson.edu/physletprob/ch7_in_class/in_class7_2/enm7_2_5.html

Current carrying loop

An electromagnet

SIM

Magnetic fields that

move across a wire create

electricity!

Faraday and electromagnetic induction

http://micro.magnet.fsu.edu/electromag/java/faraday2/

An electric motor converts electricity to motion.

An electric generator converts motion to electricity.

The Generator

http://www.wvic.com/how-gen-works.htm

Power plants create electrical

power using generators called

turbines.

Your Home

Electricity is not entirely efficient.

Sources• Bloomfield, How Things Work.• Krauskopf & Beiser, The Physical Universe. 10th ed.• Tillery, Physical Science.