MagnetismMagnetism

By Enkoosh Oyunbazar and Kinleigh O’Connor

What is Magnetism?

• Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.

• A magnet is an object that exhibits a strong magnetic field and will attract materials, like iron, to it.

• Magnets have two poles, called the north (N) and south (S) poles. Two magnets will be attracted by their opposite poles, and each will repel the like pole of the other magnet.

History of Magnetism• The Chinese and Greeks knew about the

magical properties of magnets. The ancient Greeks used a stone substance called “magnetite.” They discovered that the stone always pointed in the same direction.

• Later, stones of magnetite called “lodestones” were used in navigation.

• William Gilbert, an English physician, first proposed in 1600 that the earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.

• The term Magnetism comes from the ancient Greek city of Magnesia, where many natural magnets were found. We now refer to these natural magnets as lodestones which contain magnetite, a natural magnetic material - Fe3O4.

• Pliny the Elder (23-79 AD Roman) wrote of a hill near the river Indus that was made entirely of a stone that attracted iron.

Magnetic FieldsMagnetic Fields

• Magnetic Fields are:– The region where magnetic force exists

around a magnet or any moving charged object.

– Produced by electric currents, which can be macroscopic (seen with human eye) currents in wires, or microscopic (unable to be seen with human eye) currents associated with electrons in atomic orbits.

• Dipolar in nature. Meaning that they have a north and south magnetic pole.

• If broken, you will end up with multiple smaller magnets. The will not just have a north or south pole, they will have both.

• The SI unit for magnetic field is the Tesla (flux density), which can be seen from the magnetic part of the Lorentz force law:

• A smaller magnetic field unit is the Gauss (1 Tesla = 10,000 Gauss).

Magnetic Flux LinesMagnetic Flux Lines

• Magnetic Flux lines:Magnetic Flux lines:Are imaginary lines that map out the magnetic field

around a magnet.

Always form closed loops and never intersect.

The SI unit of magnetic flux is the weber (measures the number of lines of flux), and the unit of magnetic field is the weber per square meter, or tesla.

• Concentrated lines of flux emerge from the north pole of the magnet; curve around the magnet, and then enter the south pole of the magnet.

• The direction of the magnetic field inside the magnet is from the south to the north pole. Outside of the magnet, the field lines will go from north to south.

Magnetic Field Magnetic Field StrengthStrength

• The number of magnetic lines of flux per unit area, passing through a plane perpendicular to the direction of the lines.

• Also known as the Flux Density.

• Magnetic Field Strength is a vector quantity.

QUIZ!!!QUIZ!!!1. What is the force of attraction or repulsion of a

magnetic material due to the arrangement of its atoms? ______________.

2. Magnets have a north and south __________.3. Who proposed that the Earth itself was a magnet?

______________.4. What is the region where magnetic force exists around

a magnet or any moving charged object? ______________.

5. What is the SI unit for a magnetic field? ___________.6. What are imaginary lines that map out the magnetic

field around a magnet? _______________.7. Magnetic Field Strength is a ____________ quantity.

ANSWERS!!ANSWERS!!1. What is the force of attraction or repulsion of a

magnetic material due to the arrangement of its atoms? Magnetism.

2. Magnets have a north and south Pole.3. Who proposed that the Earth itself was a magnet?

William Gilbert.4. What is the region where magnetic force exists around

a magnet or any moving charged object? Magnetic Field.

5. What is the SI unit for a magnetic field? Tesla.6. What are imaginary lines that map out the magnetic

field around a magnet? Magnetic Flux Lines.7. Magnetic Field Strength is a Vector quantity.

• http://www.school-for-champions.com/science/magnetism.htm• http://en.wikipedia.org/wiki/Magnetism• http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html• http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/magfield.html• http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/fluxmg.html

Magnetism

By: Megan O’Connor

&Chrissy Moffatt

Background

• Magnetism was derived from Magnesia, the name of a region in Asia Minor.

• Lodestone was found, that is a naturally magnetic iron ore.

• Iron is not the only metal that is simply magnetized when positioned in a magnetic field.

Ex: Nickel and Cobalt

Basics of Magnetism

• Force of pull or repulsion that acts at a distance.

• It is caused by moving electrically charged particles in magnetic objects

example: Magnets

Magnets

• A material in which the spinning electrons of its atoms are aligned with one another= magnetic force.

• Has two ends called poles where the magnetic force is the strongest.

~North Pole ~South Pole

Electromagnets• Form magnets by using electricity

• Can be formed with a battery and copper wire coiled around a metal rod such as a nail.

Repulsion

• Two magnetic objects that have like poles facing each other, the magnetic force pushes them apart.

Attraction

• Two magnets that are unlike and close to each other, there is a force that attracts the poles together.

Magnetic Fields

• Region where magnetic force exists around a magnet or any moving charged object.

• Consists of imaginary lines of flux coming from moving or rotating electrically charged particles

• Magnetic lines do not cross

Magnetic field or lines of flux of a moving charged particle

Magnetic Field Strength

• The number of magnetic flux lines per unit area passing through a plane perpendicular to the direction of the lines; vector quantity.

• The unit of magnetic flux is Weber

Questions: 1. Magnetism derived from: a. Troad b. Pontus c. Magnesia d. Mysia

2. The spinning electrons of its atoms are aligned with one another is called a. Magnetic Lines b. Magnetic Fieldsc. Electromagnetic Force d. Magnetic Force

3. What are the two places that the magnetic forces are the strongest?

a. poles b. magnets c. particles

Questions continued…….. 4. What is the unit of magnetic flux a .joule b. weber c. coulomb d. ampere

5. Electromagnets are formed by usinga. electricity b.h2oc. fish oil d. friction

6. A magnetic field is produced by a. Stationary ions b. Stationary protonsc. Moving electrons d. Moving protons

Answers!!!!!!!!!!!!!!!!!

• 1. C• 2. D• 3. A• 4. B• 5. A• 6. C