Magnetism

1000BC Central American Indian Olmec early compass 500BCGreeks (Thales) description 500BC Indian (Sushruta) medical 350BC Chinese early compass 1050 Chinese (Shen Kuo) improved compass real use 1269 Europe (Peter Peregrinus) description 1600 Europe (William Gilbert) many experiments What we know today 1819 Europe (Oersted) connects electricity and magnetism

Magnetism All Magnets have two _________ Poles

Magnetism Would these magnets attract or repel?

Magnetism

How can a magnet exert a force on something it is not touching? Magnetic Fields

Magnetism

Strong Field Weak Field The density of field lines indicates the strength of the field

Magnetism What is the shape of the magnetic field between two like poles?

Magnetism

What is the shape of the magnetic field between two unlike poles?

Magnetism

What is the shape of the magnetic field of a horseshoe magnet?

Magnetism

Fields are three dimensional

Magnetism What is the shape of the Earth’s magnetic field?

Magnetism Are the magnetic and geographic poles in the same location?

Magnetism Currently, Earth’s south magnetic pole is located in northern Canada about 1,500 km from the geographic north pole. Angle of Declination The magnetic field reverses are random from 0.1million years to over 50million years. The last was years ago. How do we know?

Magnetism

These animals navigate with the help of the earth’s magnetic field. How? We don’t know for sure yet. Maybe you can find out

Magnetism Solar Wind

Magnetism

A magnet will not attract all objects or even all metal objects. Only a few metals, such as iron, cobalt, or nickel, are attracted to magnets or can be made into permanent magnets. What makes these elements magnetic? Magnetism

Billions of atoms align their magnetic fields to form a very small magnet. This area of alignment is called a domain

Magnetism Can a magnetic pole be isolated? Start breaking a magnet into smaller and smaller pieces

Go Past Domains

Magnetism What do you eventually get down to? A single atom

Magnetism Can a magnetic pole be isolated? Some modern theories propose the existence of magnetic monopoles. None have ever been found

Electromagnetism Oersted’s Experiment

Electromagnetism A current carrying wire produces a circular magnetic field around itself.

A current-carrying conductor produces a magnetic field around it

Electromagnetism The direction of the field can be predicted using a Right Hand Rule

Electromagnetism The direction of the field is tangent to the circle at any point

Electromagnetism What does the Field look like for a loop of wire?

Electromagnetism What does the Field look like for many loops of wire? (Coil or Solenoid)

Electromagnetism

If the solenoid is wrapped around an iron core, an electromagnet is formed. Electromagnetism

The solenoid’s magnetic field magnetizes the iron core. As a result, the field inside the solenoid with the iron core can be more than 1,000 times greater than the field inside the solenoid without the iron core. Electromagnetism

The magnetic field strength of an electromagnet increases in direct proportion to the number of turns of the coil, the current in the wire and the material in the core.

Electromagnetism An electromagnet can be used to move large quantities of metal.

Electromagnetism Faraday

Electromagnetism - When you placed a current-carrying wire in a magnetic field, the wire experiences a force. - This force acts perpendicular to both the direction of the current and the direction of the magnetic field.

Electromagnetism

Motor Walter Fendt

Current in this arm flowing from left to right. Current in the same arm reverses, flowing from right to left. Current stops flowing momentarily in the coil but inertia will propel it to make contact once again, reversing the current in the coil.

To increase the turning effect on the wire coil, we can: 1)increase the number of turns on the wire coil. 2)increase the current in the coil. 3)Insert a soft-iron cylinder at the center of the coil of wires.

Electromagnetism What happens if you move a wire in a magnetic field?

Electromagnetism You get a current in the wire

Generator A coil of wire is turned in a magnetic field generating a current.

Transformers A transformer is a device used to change the voltage in a circuit. AC currents must be used.

Transformers

The power on both sides of the transformer has to be the same. (conservation of energy) And Since P = VICombines to Give

A: Primary power lines' side B: Secondary power lines' side 1.Primary power lines 2.Ground wire 3.Overhead lines 4.Transformer for measurement of electric voltage 5.Disconnect switch 6.Circuit breaker 7.Current transformer 8.Lightning arrester 9.Main transformer 10.Control building 11.Security fence 12.Secondary power lines