Physical Science Chapters 20 and 21 - Magnetism and Electromagnetism

Magnetism

the properties of magnets and magnetic fields and the phenomena that they produce

Lodestones

could attract metal objects

Magnet

any material object that can produce a magnetic field

Magnetic Pole

one of the two regions of concentrated magnetic fields in a magnet; traditionally called the north and south poles

Magnetic Field

the region surrounding a magnet or current-containing wire that can apply a magnetic force on magnetic materials

Earth's Magnetic Field

field can be attributed to the flow of liquid iron in the outer core and extends for out into space - Prevents against solar wind and sustains life

Magnetic Declination

the difference in direction between the magnetic North Pole and the geographic North Pole

Magnetic Domain

a group of atoms whose individual magnetic fields are aligned

Ferromagnetism

the physical property in which a material's magnetic domains spontaneously align to an external magnetic field

Hans Christian Oersted

experimented with wire and compass and determined the current moving through a wire creates a circular magnetic field

Right Hand Rule

used to determine the direction of the magnetic field induced by an electric current moving through a wire

Andre-Marie Ampere

found that two parallel wires carrying current in the same direction are magnetically attracted

Solenoid

a coil of current-carrying wire used as a magnet

William Sturgeon

observed that placing a ferromagnetic bar inside a solenoid greatly increased the force of its magnetic field (by 20x)

Electromagnet

the combination of a strong magnet and an electrified wire coil

Electromagnetic Induction

the creation of an electromotive force (EMF) by way of moving a magnetic field around an electric conductor, and the creation of current by moving an electric conductor through a static magnetic field

Applications for Electromagnets

1). Moving and sorting metals 2). Magnetically levitated trains 3). MRI machines 4). Particle accelerators

Generators

a device that converts mechanical energy into electrical energy by electromagnetic induction

AC Generators

rotates wire coils within a magnetic field or rotates a magnet within wire coils

Rotor

rotating part

Stator

stationary part

Prime Mover

part that provides mechanical energy to turn the rotor

DC Generators

similar to AC generators

Commuter

part that allows current to flow from the generator in only one direction

Electric Motors

motors function like generators, but in reverse order - Instead of using magnetic fields or coils to turn a rotor inside a stator, motors use electricity to cause the interaction between the magnetic fields of the magnet and wire coil's current to turn the rotor

Transformers

a device that uses electromagnetic induction to increase or decrease the voltage of an AC current - Coils are wrapped around an iron frame to allow for more efficient induction between the coils

Step-Up

has more output coils than input and increases voltage

Step Down

has more input coils than output and decreases voltage

Electromagnetic Wave

a disruption in an electromagnetic field that carries energy, even through the vacuum of space

Sir Isaac Newton

discovered he could form a rainbow by using a prism to disperse light - he did not know that light was related to electrostatic or magnetic forces

Andre Ampere

suggested the combination of electricity and magnetism in 1820

James Maxwell

published mathematical equations showing this relationship between electricity and magnetism- Electric and magnetic fields interact in a wave like fashion - Suggested that light moves as a disturbance in these fields

Speed of Electromagnetic Waves

some scientists thought that light moves instantaneously - 1676, Ole Romer proved this wrong by studying the time it took light to travel to Jupiter and back to Earth and how it varied based on orbits - Indicated that light moved at a finite speed

Albert Michelson

known for calculating the speed of light -Used a 1.6 km long vacuum tube with light sources, mirrors, and sensors and made a beam of light move through the length of the tube ten times - Light travels slower in other materials

Electromagnetic Wavelength and Frequency

the vibrations of the source determine the frequency of the wave - The frequency does not change as light enters a new medium - When EM waves enter a denser material, they slow down, causing a shortening of the wavelength

Energy of Electromagnetic Waves

energy of waves relates to the amplitude - EM waves do not displace matter, so they cannot be measured directly - Max Planck determined that photons directly relate to the frequency of the wave

Photon

a wave bundle, or particle, of electromagnetic energy

Intensity of Electromagnetic Waves

the intensity of EM waves relates to how close the observer is to the source

Wave Model

Thomas Young proved light behaved like a wave - Hypothesized that if the light acted as a particle, he would see two bright bands on the second screen, one for each slit - If they acted as waves, each slit would diffract light waves that would interfere with one another

Particle Model

Heinrich Hertz found that particular metals will emit electrons only if the light is of high enough frequency

Wave-Particle Density

all EM energy travels as photons, so it travels as both waves and particles

Electromagnetic Spectrum

the collections of all the electromagnetic waves

Microwaves

a subsection of radio waves (Frequency: 300 MHz or 300 Ghz; Wavelength: 1 m to 1 mm; Uses: navigation, communication, astronomy, cooking)

Radio Waves

the longest electromagnetic waves (Frequency: 3 Hz to 300 GHz; Wavelength: 100,000 km to 1 mm; Uses: navigation, communication, astronomy)

Infrared Waves

are waves located between microwaves and visible light. Their name relates to their position just below the red wavelengths of visible light (Frequency: 300 GHz to 430 THz; Wavelength: 1 mm to 700 nm; Uses: astronomy, medical imaging, wireless devices - some animals can detect infrared waves)

Visible Light

the collection of electromagnetic waves that we can see - the special design of our eyes allows us to see these waves (Frequency: 430 THz to 790 THz; Wavelength: 700 nm to 380 nm)

Ultraviolet Waves

waves that are just beyond the violet waves of the visible spectrum (Frequency: 790 THz to 30 PHz; Wavelength: 380 nm to 10 nm; Uses: medical treatment, dentistry, killing bacteria)

X-Rays

high-energy waves that were discovered accidentally by Wilhelm Rontgen (Frequency: 30 PHz to 30 EHz; Wavelength: 10 nm to 10 pm; Uses: medical imagery, transportation security, nondestructive inspection)

Gamma Rays

the highest-energy electromagnetic waves that are emitted during radioactive decay and from sources in space (Frequency: above 30 EHz; Wavelength: 10 pm down to 1 fm; Uses: medical treatment, astronomy)

Speed of Electromagnetic Waves

c = f𝜆, where c is the constant 3.00 x 10^8

Energy of Electromagnetic Waves

E = hf, where h is Planck's constant 6.62607015 x 10^-34