Categories: All - current - induction - field - magnetism

by privut purson 15 years ago

3295

Magnetism

The principles of magnetism and electromagnetism are essential in understanding how magnets and electric currents interact. Natural magnets like lodestone and artificial permanent magnets such as Alnico are significant due to their ability to lift objects much heavier than steel.

Magnetism

Magnetism

Magnetic Classification

Non-magnetic
Ex: Wood,Glass,Plastic
Paramagnetic - Feebly Attracted
Ex: Platinum
Ferromagnetic - Strongly Attracted
Ex: Alnico - Alloy of Aluminum, Nickel, Cobalt
Ex: Iron, Cobalt, Nickel

Retentivity = Ability of Magnet to Resist Demagnetization

Permeability = Ease Which Material Is Magnetized

Laws

Force of Attraction / Repulsion Does NOT Follow Inverse Square Law
Like Repel / Unlike Attract
Two Poles
South
North

Magnets

Electromagnets
Artificial Permanent
Alnico - Alloy of Aluminum, Nickel, and Cobalt

Many Times Lifting Capacity of Steel

Compass Needle
Natural
Lodestone (Iron Oxide)(Magnetite)

Ability of Certain Materials To Attract Iron, Cobalt, or Nickel

Electromagnetism

Electromagnet
Helix =Wire Coil

Solenoid : Helix Carrying Current

Solenoid With Iron Core=Electromagnet

Magnetic Flux : Magnetic Lines of Force
Branch of Physics deals with Relationship of Electricity/Magnetism
Elctromagnetic Induction

Moving Magnetic Fields Induce Electron Current

When Conductor (Wire) Cuts Across Magnetic Flux (or Is Cut By Magnetic Flux) An EMF [ Electromagnetic Force] or Potential Difference is Induced In Conductor

Flux Line : Interaction Between A Single Loop Conductor and A Line of Force

Magnitude : Size of Induced EMF

Number of Turns In Conductor Coil

Induced EMF Is Directly Proportional To # of Turns In Coil

Lines of Each Turn of Coil Are Additive = More Flux Linkages Per Second

Angle Between Conductor/Magnetic Field

As Angle Approaches 90 Degrees

Space Between Lines of Force Become Smaller

More Flux Lines Are Cut Per Second

Larger EMF Is Induced

Strength : Stronger The Magnetic Field, The Higher The Induced EMF

Speed : More Flux Lines Cut Per Second, Higher The Induced EMF

3 Ways To Induce An EMF

Flux May Vary In Strength While Stationary Wire Lies Within It

Flux May Move Across Stationary Wire

Wire May Move Across Stationary Flux

Magnetic Field Always Surrounds Conductor With Flowing Current

Field Only Exists While Current Flows

Left Thumb Rule: Wire Held in Left Hand

Fingers Encirlcing Wire Indicate Direction of Magnetic Lines Around Current

Thumb Points Direction of Current ( + or - )