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 N S 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 N S 8

V. Magnetic Field Lines Like Poles S N N S 9

VI. Magnetic Field Strength (Magnetic Flux) V. Magnetic Field Lines Unlike Poles N S N S VI. Magnetic Field Strength (Magnetic Flux) Field is strongest where lines are ___________ ( ) MOST DENSE CLOSEST TOGETHER 10

Earth’s Magnetic Field (7 min) V. Magnetic Field Lines Earth’s Magnetic Field (7 min) 11

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 12

VII. Magnetic Fields Created by Current Carrying Wires Note: Farther you move away from wire, weaker the magnetic field 13

VIII. Force on a Current in a Magnetic Field Current carrying wire are essentially _______________ B. Moving electrical charges experience a ________________ if placed in a __________________ MOVING ELECTRICAL CHARGES MAGNETIC FORCE MAGNETIC FIELD 14

VIII. Force on a Current in a Magnetic Field Jumping wire demo 15

VIII. Force on a Current in a Magnetic Field C. Direction of Force (LHR) Thumb points in direction of __________ Fingers point in the direction of __________ Palm points in the direction of ___________ Jumping wire demo Current (e-) Magnetic Field Magnetic Force 16

IX. Inducing a Current 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 _______ in the wire induces (creates) current 17

X. 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 18

XI. 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 19

XII. Magnetic Forces on Charged Particles Moving charges ____________   If a charged particle moves through a magnetic field, it will experience a ___________________ Cathode Ray Tube TV with Magnet Deflection Demo (1 min) CREATE MAGNETIC FIELDS MAGNETIC FORCE 20

A. Direction of Magnetic Force (Right Hand Rule) magnetic field 1. Point fingers in the direction of _____________________   2. Point thumb in direction of _______________________ 3. Palm points in the direction of ____________________ moving + charge magnetic force **NOTE** For __________ charges, use _______ hand (force is in the ___________ direction) negative left opposite 21

1. Charge must be _________________ Rules: 1. Charge must be _________________   Velocity of moving charge must have a component _______________ to the direction of the __________________ moving perpendicular perpendicular magnetic field 22

XIII. Magnetic Field in 3D 23