Unit 12 Magnetism

I. Applications of Magnetism Credit cards, electric motors, MRI scanning, Maglev Trains, car alternator 2

II. Review of Electric Field Electric Field - Created by objects that have a _________ charge Electric Force - Experienced by charges within an ____________ electric field What happens if the charges are moving…? 3

The ___________ of __________ particles creates a _____________ MOTION III. Cause of Magnetism The ___________ of __________ particles creates a _____________ MOTION  CHARGED  MAGNETIC FIELD  A. Magnetic Domains: ALIGNED ATOMS Clusters of ________________ Each domain is perfectly magnetized and is made of billions of aligned atoms 4

Becomes a magnet when domains line up. III. Cause of Magnetism Becomes a magnet when domains line up. 5

B. Ferromagnets: Naturally Occuring Magnets III. Cause of Magnetism B. Ferromagnets: Naturally Occuring Magnets Examples: Iron, Nickel, Cobalt, magnetite Created by: 1. Leaving ferromagnetic material in a strong magnetic field 2. Running an electrical current through a conductor 6

Every magnet has two poles: Called North and South IV. Laws of Magnetism Every magnet has two poles: Called North and South 2. Like poles repel ( N near a N or S near a S)  And opposite poles attract ( N near a S) 3. Magnetic poles on a magnet cannot be separated 7

V. Magnetic Field Lines Characteristics: Magnetic field lines form loops around magnet 2. Lines go from North to South 3. Closer the field lines are, stronger the magnetic field is 4. Lines NEVER OVER LAP 8

V. Magnetic Field Lines Like Poles 9

VI. Magnetic Field Strength (Magnetic Flux) V. Magnetic Field Lines Unlike Poles VI. Magnetic Field Strength (Magnetic Flux) Field is strongest where lines are ___________ ( ) Earth’s Magnetic Field (7 min) MOST DENSE CLOSEST TOGETHER 10

VII. Magnetic Fields Created by Current Carrying Wires A current carrying wire carries _____________, therefore it creates a _________________ Oersted Demo Bose Electromagnetic Suspension (never used due to cost and weight) CHARGES (e-) MAGNETIC FIELD 11

VII. Magnetic Fields Created by Current Carrying Wires Note: Farther you move away from wire, weaker the magnetic field 12

VIII. Charge Moving through a Magnetic Field When a charged object moves through a magnetic field its experiences a ___________   This is the principle behind _______________ and __________________ MAGNETIC FORCE TELEVISIONS (video) PARTICLE ACCELERATORS 13

IX. Current-Carrying Wire in Magnetic Field When a current-carrying wire is placed in a magnetic field it also experiences a  ________________ This is the principle behind ______________ and ___________________   MAGNETIC FORCE ELECTRIC MOTORS SPEAKERS How a speaker works 14

X. Inducing a Current in the wire current creates generators A current in a wire produces a magnetic field surrounding the wire. Question: Can a magnetic field cause a current to be induced in a wire? Conceptual Development: phet simulation Electrons in the wire experience a magnetic force and are pushed _________________ Movement of the electrons _____________ a _______ Principle behind _______________ and _______________________ in the wire current creates generators power plants 15

XI. How do we create this Current (Faraday's Law)? 1. Move a coil in and out of a magnetic field 2. Rotate a coil in a magnetic field 3. Vary the intensity of the magnetic field 16

XII. How do we gain Maximum Current 1. Wire must be perpendicular to field 2. Increase number of coils of wire 3. Increase speed of wire or magnet 4. Increase the strength of magnetic field 17