Ch 14 Magnetism I Characteristics of Magnets w

Ch. 14 - Magnetism I. Characteristics of Magnets w Magnetism w Magnetic poles w Magnetic field w Magnetic domain

A. Magnetism Ø Magnetism w force of attraction or repulsion between unlike or like poles w due to the arrangement of electrons w closely related to electricity

B. Magnetic Poles Ø Magnetic Poles w like poles repel w unlike poles attract w a broken magnet creates new poles

C. Magnetic Field Ø Magnetic Field w area around a magnet where magnetic forces act w field lines show direction of field (N S)

D. Magnetic Domain Ø Magnetic Domain w groups of atoms with aligned magnetic poles domain w in a magnetized object, domains are all aligned

Ch. 14 - Magnetism II. Uses of Magnetic Fields w Electromagnet w Speaker w Motor

A. Electromagnet Ø Electromagnet w strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core w acts like a bar magnet when current is on

B. Speaker Ø Speaker w electrical energy mechanical energy w wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet w forced vibration causes the cone to move sound

C. Motor Ø Motor w electrical energy mechanical energy w electromagnet rotates between the poles of a fixed magnet w commutator reverses the poles of the e’magnet

C. Motor assembled motor brushes & wires to battery armature & commutator field magnet

Ch. 14 - Magnetism III. Producing Electric Current w Electromagnetic Induction w Electric Generator w DC & AC w Transformer

A. Electromagnetic Induction Ø Electromagnetic Induction w producing a current by moving a wire through a magnetic field w some microphones work just like minispeakers in reverse w sound waves cause coil to move current Coil Dynamic Microphone

B. Electric Generator Ø Electric Generator w mechanical energy electrical energy w armature is rotated between magnet poles w magnetic field induces a current in the wire coil GENERATOR MOTOR

B. Electric Generator Ø Hydroelectric Dam w PE of lake water is converted to KE w mechanical KE turns the generator shaft which creates electrical energy

C. DC & AC Ø Direct Current (DC) w current flows in one direction w dry cells Ø Alternating Current (AC) w current reverses its direction at regular intervals w electrical outlets

D. Transformer Ø Transformer w increases or decreases AC voltage w primary coil AC produces a magnetic field that induces AC in the secondary coil w voltage ratio = ratio of turns in each coil

D. Transformer Ø Step-up Transformer w increases the voltage w more turns w power plants Ø Step-down Transformer w decreases the voltage w fewer turns w household appliances (hairdryers, etc. )

Ch. 15 - Light I. Electromagnetic Radiation Ø EM Spectrum Ø Types of EM Radiation

A. EM Radiation Ø Electromagnetic Radiation w transverse waves produced by the motion of electrically charged particles w does not require a medium w speed in a vacuum = 300, 000 km/s w electric and magnetic components are perpendicular

A. EM Radiation Ø Photons w tiny, particle-like bundles of radiation w absorbed and released by electrons w energy increases with wave frequency

B. EM Spectrum long short low f high f low energy high energy

C. Types of EM Radiation Ø Radiowaves w lowest energy EM radiation

C. Types of EM Radiation Ø Radiowaves w FM - frequency modulation w AM - amplitude modulation ØMicrowaves w penetrate food and vibrate water & fat molecules to produce thermal energy

C. Types of EM Radiation Ø Infrared Radiation (IR) w slightly lower energy than visible light w can raise thermal energy of objects w thermogram - image made by detecting IR radiation

C. Types of EM Radiation Ø Visible Light w small part of the spectrum we can see w ROY G. BIV colors in order of increasing energy red R O Y G. orange green yellow B blue I indigo V violet

C. Types of EM Radiation Ø Ultraviolet Radiation (UV) w slightly higher energy than visible light w Types: • UVA - tanning, wrinkles • UVB - sunburn, cancer • UVC - most harmful, sterilization

C. Types of EM Radiation Ø Ultraviolet Radiation (UV) w Ozone layer depletion = UV exposure!

C. Types of EM Radiation Ø X rays w higher energy than UV w can penetrate soft tissue, but not bones

C. Types of EM Radiation Ø Gamma rays w highest energy EM radiation w emitted by radioactive atoms w used to kill cancerous cells Radiation treatment using radioactive cobalt-60.