Topic: electricity and magnetism

topics > Group: science

atoms and molecules
electromagnetic field
quantum electrodynamics
special relativity
Subtopic: electromagnetism up

Quote: electricity, whatever may be its source, is identical in its nature [»faraM_1839, OK]
Quote: the various forms under which the forces of matter are made manifest have one common origin [»faraM_1855, OK]
Quote: magnetism grew from an occult power with limited domain to a central, universal force [»faraM_1855, OK]

Subtopic: atomic interaction as electrical up

Quote: the ultimate basis of interaction between atoms is electrical [»feynRP_1963]
Quote: the energy of the atomic bomb is really electrical energy that is released when electrical forces overcome the nuclear forces [»feynRP_1964]
Quote: electrical force holds atoms and molecules together; at the scale of atoms, electrical forces are not balanced [»feynRP_1964]
Quote: balanced electrical charges do not attract at a distance; but at short scales, the charges rearrange and generate strong interactions

Subtopic: electricity vs. gravity up

Quote: the ratio of electrical and gravitation force between two electrons is independent of distance; it is 1 divided by 4.17 x 10^42! [»feynRP_1963]
Quote: the electrical force is a billion-billion-billion times stronger than gravity; its positives and negatives balance almost perfectly forming tight, fine mixtures [»feynRP_1964]
Quote: electricity is a much stronger force than gravitation [»feynRP_1963]
Quote: Faraday failed to unify gravity and electricity

Subtopic: chemistry as electrical up

Quote: many chemical effects can be understood via electrical forces; e.g., a colloid consists of small charged particles suspended in water; salt neutralizes the charge and allows coagulation [»feynRP_1964]

Subtopic: superconductor up

Quote: superconductors provide direct access to the quantum nature of matter [»meadCA6_1997]
Quote: a superconductor is in a coherent state of the collective interaction of free electrons; each electron depends on the states of the entire ensemble
Quote: with superconductors, understand quantum effects via waves

Subtopic: electric charge up

Quote: electric charge is conserved, i.e., it is indestructible [»feynRP_1964]
Quote: the charge of an electron is independent of its speed, but the charge density of moving electrons varies like the relativistic mass of a particle [»feynRP_1964]
Quote: because Coulomb's force law is exactly the inverse square, a thin spherical shell of charge is like a point charge outside the shell and zero inside the shell [»feynRP_1964]

Subtopic: electricity through a solid up

Quote: a solid conducts electricity by propagating a wave packet of probability amplitudes from atom to atom [»feynRP_1965]
Quote: in a perfect lattice, electrons can easily travel through a crystal without scattering; allows metals to conduct electricity and transistors to imitate the radio tube [»feynRP_1965]
Quote: connected harmonic oscillators and atoms in a crystal will convey an irregularity as a wave [»feynRP_1965]

Subtopic: electricity through a liquid up

Quote: most liquids conduct electricity; water is the feeblest; use to study matter [»faraM_1839, OK]
Quote: Faraday named anode, cathode, anions, cations, ion, and electrolyte [»faraM_1839, OK]

Subtopic: electrical conductor up

Quote: by Gauss' law, the charge density is zero inside any conductor; any excess charge is within one or two atomic layers of the surface with the electric field normal at the surface [»feynRP_1964]
Quote: shielding: any static distribution of charges inside a closed conductor can not produce any fields outside, and vice versa
Quote: the electric fields sufficiently inside a closed screen are zero, just like a closed metal sheet [»feynRP_1964]

Subtopic: semiconductor up

Quote: dope a semiconductor with donors and acceptors of electrons; the electrons and electron holes are free to wander [»feynRP_1965]
Quote: the average density of electrons in a semiconductor must equal the density of donor sites; otherwise electrical charge does not balance
Quote: a transistor consists of two semiconductor junctions with a very thin region between them; holes, or electrons, can diffuse across the gap [»feynRP_1965]
Quote: a transistor is an amplifier: a small current at the base electrode gives a 100-fold larger current at the collector electrode

Subtopic: balanced charges up

Quote: if two grains of sand were 30 meters apart and all electrical forces were attractive, there would be three million tons of force between them
Quote: for nonpolar molecules the electrical attraction at large distances varies inversely as the seventh power of the distance; dipolars have greater attraction [»feynRP_1963]
Quote: if two people at arm's length had 1% more electrons than protons, their repulsion would be enough to lift the earth [»feynRP_1964]

Subtopic: dipole up

Quote: a dipole is a close pair of electric charges; they occur commonly, e.g., water [»feynRP_1964]
Quote: a dipole's electric field decreases as 1/r^3 and is twice as strong on the axis as at 90 degrees to the axis
Quote: at a distance, any neutral collection of charges acts the same as a dipole
Quote: a dielectric or insulator contains many dipoles; these are attracted to charged objects at the square of the electric field [»feynRP_1964]

Subtopic: condenser up

Quote: to get a large condenser use a big area and a small separation, e.g., roll wax paper and aluminum foil for a radio-type condenser [»feynRP_1964]

Subtopic: electrical ground up

Quote: for a ground, Faraday used the house gas pipes, public gas pipes, and water pipes; needed for many experiments [»faraM_1839, OK]

Subtopic: electrical generator up

Quote: the generators at Boulder Dam turn thousands of little wheels throughout the whole city; such an effect exists nowhere else in nature [»feynRP_1964]
Quote: if rotate a cooper disk between two magnets, generate a current between axis and rim [»faraM_1839, OK]
Quote: invert a helix to demonstrate the direct magneto-electric induction of the earth [»faraM_1839, OK]
Quote: a revolving copper plate is a new electric machine for any of the ordinary applications of electricity [»faraM_1839, OK]
Quote: use the earth's uniform magnetic field to demonstrate that a moving wire generates current in proportion to the magnetic force [»faraM_1855, OK]
Quote: a moving wire generates electricity in proportion to the number of lines of force cut
Quote: in a uniform field, a moving wire generates electricity in proportion to its velocity, length, and mass

Subtopic: lightening up

Quote: the electric potential across the earth's atmosphere is 400,000 volts with a total electric current of 700 megawatts [»feynRP_1964]
Quote: the upper atmosphere is almost a perfect conductor
Quote: thunderstorms recharge the atmosphere with electrons
Quote: measure the electrical potential of the atmosphere by a bucket of water with a small leak
Quote: light travels faster than sound so we see the lightening before hearing the thunder, despite both having the same cause [»lucr_55]
Quote: it is foolish to understand the thunderbolt as a hidden purpose of the gods; why are the innocents hurt, why is lightening wasted on deserted places, why provide a warning? [»lucr_55]
Quote: why does lightening favor the mountain peaks and higher places?

Related Topics up

Topic: atoms and molecules (57 items)
Topic: chemistry (11 items)
Topic: electromagnetic field (63 items)
Topic: light (46 items)
Topic: physics (51 items)
Topic: quantum electrodynamics (34 items)
Topic: special relativity
(73 items)

Updated barberCB 3/06
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