Magnetism

Magnetic dipole

fundamental unit of magnetism; both a north and south pole together

Magnetic field lines

come out of the north end and go into the south end

Ferromagnetic

describes a material that become permanent magnets when exposed to a strong magnetic field; ex. iron, nickel

Paramagnetic

describes materials that can become magnetized only as long as there is a surrounding magnetic field

Magnetic fields

produced by moving electrically charged particles

Hans Christian Oersted

noticed that a wire with current running through it would deflect a compass

Right-hand rule

thumb points in direction of current, fingers curl in the direction of the magnetic field

Magnesia

coastal district in Greece where iron-attracting lodestones were found

Compass

points north due to Earth’s magnetic field, usually consists of a small piece of magnetic iron floating in a liquid

Dynamo effect

the Earth generate electric currents through its molten core as it spins

Reversal of polarity

magnetic poles switch every 1k or 100k years; can be seen in alternating patterns in the magnetism of the seafloor

Plasma

gas so hot that the nuclei cannot hold onto any electrons, creates strong electric currents and strong magnetic fields

Sunspots

cool spots of the Sun that are formed when the Sun’s magnetic field gets twisted and cuts off patches of its surface from the rest of it

Polarity reversal on the sun

happens every 11 years, causes lots of sunspots to appear

Coronal mass ejections

when chunks of the Sun’s surface are ejected due to its magnetic field getting so twisted and stretched out

Carrington Event

a particularly big CME that created extremely bright aurora activity and global electrical disturbances

Solar wind

individual protons and electrons that are released from the Sun; get deflected by the Earth’s magnetic field

Aurora

forms when solar wind breaks apart atoms into ions that then capture stray electrons, releasing energy in the form of light (O glows green, H glows purple)

Neutron stars

exposed cores of very massive collapsed stars, have the most extreme magnetic fields due to their rapid rotation

Mars’ magnetic field

incredibly weak, couldn’t protect Mars from solar wind, causing it to lose its atmosphere and water

Equation for magnetic force

F=qvB

B

strength of the magnetic field, measured in teslas

Strength of Earth’s magnetic field

25-65 microteslas

Direction of magnetic force

perpendicular to the magnetic field and the velocity of the particle

Deflection

whenever a particles velocity changes direction, the force exerted on it also changes direction, deflecting it in a circle

Centripetal force

force that only changes an object’s direction, not its speed

Mass spectrometer

used to determine a sample’s atomic composition; sample is vaporized, ions are accelerated by a voltage, ions are moved into magnetic field and deflected; where they land depends on charge and mass

Ampere’s law

used to determine magnetic field of objects; B=(μI)/2πr

Amperian loop

circle with radius r that goes around a current-carrying wire

μ

permeability of free space

Solenoid

multiple circular loops on top of each other; has a magnetic field similar to a bar magnet

Magnetic field in a solenoid

B=μI(N/L)

Teslas

unit for strength of magnetic fields

Michael Faraday

young bookbinder who became interested in electricity after attending public lectures, worked as Humphrey Davy’s lab assistant, studied connection between electricity and magnetism

Humphrey Davy

famed chemist

Christmas Lectures

public lectures at the Royal Institution, tradition started by Faraday; broadcasted by the BBC

Faraday’s Law

moving a magnet near a coil of wire will induce a voltage in the wire; V=−N(ΔΦ/Δt)

Magnetic field flux

Φ; how much magnetic field there is passing through a given area (area of a loop of wire)

Generator

any device that converts mechanical motion into electrical energy

Motor

a device that turns electrical energy into mechanical motion

Lenz’s Law

negative sign in Faraday’s Law; moving magnet turns solenoid into its own magnet, magnetic field created by solenoid will be whatever it needs to be to oppose the external change

Transformer

device that reduces voltage to safer levels

Alternating current

current that constantly switches directions, creates a magnetic field that switches directions, which induces a current

Voltage in secondary coil

V₁/N₁=V₁N₂

Power

P=IV

Diode

device that allows current to flow through it in only one direction

Voltage for AC

varies gradually; when loop is perpendicular to field, you get max flux, when it is parallel, you get zero flux

Capacitor

can smooth out the bumps in a current by charging up when it flows one way and discharging when it flows the other way

Inductor

solenoid attached to the circuit on either end; resists changes in current in the electric circuit

Self-induction

short burst of current is created by inductor to oppose a reduction in current

Frequency of circuit oscillation

f=1/2π√LC

Magnitude of Oscillation

if there is a driving force with the same frequency as a system’s resonant frequency, system will oscillate with a greater magnitude

Frank Hauksbee

invented the first electric light in 1705

Barometric light

mercury barometer that, when shaken, caused the mercury to shed electrons onto the interior of the glass container, ionizing the gas inside and creating light

Humphrey Davy

invented the arc lamp

Arc lamp

first electric light to see widespread use, creates a large enough voltage between two pieces of metal to result in dielectric breakdown, generating a mini lightning bolt

Incandescent lights

emit light by causing a solid object to heat up enough that it glows

Thomas Edison

first to build an entire infrastructure around powering light bulbs in cities

George Westinghouse

founded his own electric company, used alternating current to produce light

Mikhail Dolivo-Dobrovolsky

invented a three-phase generator

Three-phase generator

allowed an efficient transfer of current over long distances using AC

Alexander Just & Franjo Hanaman

inventors of the tungsten lightbulb

Tungsten lightbulb

more efficient and longer-lasting than carbon light bulbs and became the international standard

Nikola Tesla

worked for Edison’s electric company in his early career, invented the Tesla coil

Tesla coil

creates a voltage on a metal ball on top of a coil of wire that is high enough to shoot lightning bolts into the air