Magnetism and Uses Goals: magnetism, source, types, electromagnetism, magnetic materials, force calculations, motors, generators and transformers

Magnetism  Magnetism – field force with north and south poles  Alignment of magnetic domains  Domains- groups of atoms with magnetic fields that complement one another  Atoms exhibit magnetic properties because of the spin of an unpaired electron (moving electric field) (fourth quantum number)  Opposite poles attract and the same poles repel  Field lines point away from North and toward the South pole

Types of Magnets  Permanent and an Electromagnet  Permanent – hold magnetic properties domains are aligned bar and horseshoe  Magnetized in an electric current or a strong magnetic field  Unmagnetized by shock, heat or another field  Diamagnetic- fields cancel no magnetism Pb  Paramagnetic- atoms are magnetic but not domains Al

 Nonmagnetic- when permanent magnet is removed there is no magnetism  Ferromagnetic – strong magnetic properties Fe Ni Co Nd  Earth and Stars  Electromagnets – coil with an iron core  Advantages – turned on and off and vary the magnetic strength (lab)  Turns in the coil current size of core  Why? Current - carrying conductor has a magnetic field around it Right Hand Rule  Oersted’s discovery- with a compass and current discovered that the current produced a magnetic field reversed by reversing the current direction

Electromagnetism  Magnetism produces electricity and electricity produces magnetism  Faraday – law of induction  Electric motors and Generators  Home wiring AC, current in opposite directions repel magnetic fields in the same direction attract  Motors – electrical to mechanical energy  Electromagnet in the core of the motor is pushed by the field of the electromagnet continually as the magnetic field is reversed easier in AC  Parts include armature (moving electromagnet), rotor, brushes, permanent magnet and commutator (switch) (Lab)

 Generator – electric motor in reverse  Mechanical energy into Electrical  Energy easily moved by conductors and easily converted to another form  Moving coil of wire within a magnetic field induces a current in the wire  Produces AC because of the switch in direction of magnetic fields in the permanent magnets  Faraday’s Law of Induction – faster the solenoid turns in the magnetic field the higher the voltage  Turbine forced to turn by wind, falling water, and expanding steam from burning coal or nuclear power

 Transformers – step-up or step-down voltage to efficiently by increasing or decreasing the number of coils around an iron core  V1 x N2 = V2 x N1

Magnetic Field Strength  Electric fields produce electric force per unit of charge E = k qq/r² E = N/C  Magnetic fields produce magnetic force per unit of charge depending on velocity B = F magnetic / q v B = N/C m/s T  F mag = B q v  Magnetic Field produced by current B = F magnetic/ I x L B = N/C/s m T

Uses of Magnetism  Solenoids, speakers, doorbells, galvanometers, motors and generators, ignition coils, CAT scans and MRI…….

Electromagnetic Waves  Electromagnetic Wave – transverse wave of electromagnetic radiation  Energy is stored in electric and magnetic fields and transferred in the form electromagnetic waves  Oscillating electric and magnetic fields propagated perpendicular to one another  Produced by an exited electron (electric field) returning to ground state  Quantized (Plank) Photon (Einstein)  Dual Nature – Particle and Wave-like