Topic: electromagnetic field

topics > Group: science

electricity and magnetism
quantum electrodynamics
Subtopic: understanding electromagnetism up

Quote: it is harder to understand the electromagnetic field than to understand invisible angels; the former requires a vivid imagination of a myriad of complex waves [»feynRP_1964]
Quote: magnetism grew from an occult power with limited domain to a central, universal force [»faraM_1855, OK]
Quote: are magnetic lines of force the correct abstraction for magnetism [»faraM_1855, OK]
Quote: compare Searle's Chinese room argument to an argument against light as electro-magnetism [»churPM1_1990]

Subtopic: electricity and magnetism up

Quote: Maxwell realized that light, electricity, and magnetism were the same phenomena; one of the great unifications of physics
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: electricity and light up

Quote: electric current around a ray of polarized light rotates the light in the same direction [»faraM_1855, OK]
Quote: Faraday magnetized and electrified a ray of light and illuminated a magnetic line of force

Subtopic: magnetism and relativity up

Quote: magnetism is a relativistic effect; for electrons moving in parallel wires the relativistic correction is 10^-25 [»feynRP_1964]
Quote: when relativity was discovered, the electromagnetic laws already accounted for relativistic effects
Quote: associated with a vibrating electric field is a vibrating magnetic field at right angles and 1/c of the intensity of the electric field [»feynRP_1963]

Subtopic: electromagnetism and measurement up

Quote: describe electrical phenomena in terms of measurements, methods of measurement, and standards
Quote: Maxwell developed his theory in cartesian coordinates and promoted the use of quaternion or vector equations
Quote: use a galvanometer to measure electricity

Subtopic: electromagnetism and quantum mechanics up

Quote: use vector and scalar potentials for introducing electromagnetic effects into quantum descriptions; avoids the use of force concepts
Quote: a magnetic or electrical field changes the phase of the probability amplitude to arrive via any trajectory by the space or time integrals respectively [»feynRP_1964]
Quote: the amplitude to find an electron with some momentum has the same form as the amplitude to find an electron at some location; only the width of the Gaussian is different [»feynRP_1965]
Quote: the width of the Gaussian distributions of an electron's probability amplitude leads to a quantitative statement of the Heisenberg uncertainty principle
Quote: derive standard results of electromagnetic theory from macroscopic quantum systems; without Maxwell's equations, traditional quantum formalisms, or correspondence limits [»meadCA6_1997]

Subtopic: atomic field up

Quote: can use Gauss' law to approximate the electrical field inside an atomic nucleus [»feynRP_1964]

Subtopic: field up

Quote: a field is any physical quantity which takes on different values at different points in space; e.g., electrical and magnetic fields; values may be scalars or vectors [»feynRP_1964]
Quote: any simple, spatial physical problem, or simplification of a complicated problem, must look like electrostatics

Subtopic: electromagnetic field up

Quote: electricity and magnetism are lines of force at right angles to each other [»faraM_1855, OK]
Quote: through lines of force, the smallest atom of matter on earth acts directly on the smallest atom of the sun or comet [»faraM_1855, OK]
Quote: electro-magnetic fields knit together the universe because they vary inversely to the first power of the distance instead of the inverse square [»feynRP_1963]
Quote: electric and magnetic forces are part of one physical phenomenon; e.g., the magnetic force on a charge moving along a wire is the same as the electric force of a wire moving past a charge [»feynRP_1964]
Quote: an electromagnetic field is real because it can possess momentum and energy
Quote: principle of superposition of electrical fields: the total field due to all sources is the sum of the fields due to each source [»feynRP_1963]
Quote: principle of superposition: the electric and magnetic fields produced by a set of charges is the same as their sum over each charge [»feynRP_1964]
Quote: the deflecting force of electric current is directly proportional to the absolute quantity of electricity passed [»faraM_1839, OK]
Quote: the electric field is the sum of the individual fields and the field of a single charge is given by its acceleration retarded by the speed c [»feynRP_1963]

Subtopic: Maxwell's equation up

Quote: the propagation of energy takes place through a medium; Maxwell's goal was an accurate, mental representation of this medium [»maxwJC_1891, OK]
Quote: Maxwell's equation for electrical force has three terms: an inverse square term for Coulomb's law, an inverse square correction for delay, and an inverse term for radiation [»feynRP_1963]
Quote: the electromotive intensity depends on the velocity of a particle transverse to the magnetic field, the time-variation of the magnetic field, and the time-variation of the electric field [»maxwJC_1891, OK]
Quote: the electrical force on a charge depends only on its position, velocity, and size; the equation of force is in terms of the electrical and magnetic fields which vary by position and time [»feynRP_1964]
Quote: measure the speed of propagation of electromagnetic fields by measuring the forces between two unit charges and between two unit currents; same as the speed of light [»feynRP_1964]
Quote: Maxwell realized that light, electricity, and magnetism were the same phenomena; one of the great unifications of physics
Quote: from Maxwell's equations: fields generated by moving charges can leave the sources and travel alone through space even after all activity has stopped and the charges are zero [»feynRP_1964]

Subtopic: electromagnetic wave up

Quote: for any electromagnetic wave, the magnetic and electrical fields are perpendicular to the direction of motion, the fields are mutually perpendicular, and the magnitude of the electric field is c times that of the magnetic field [»feynRP_1964]
Quote: although electrical force goes inversely as the distance squared, a shaking charge conveys influence much farther out [»feynRP_1963]
Quote: the electromagnetic field conveys the vibrations of electrical force like water conveys waves
Quote: in water, one cork can move another much further away by jiggling than by pushing; same with charges in an electromagnetic field
Quote: the only difference between electromagnetic waves is the frequency of oscillation [»feynRP_1963]
Quote: since ratio of the area of the surface of a cone to the kinetic energy due to an electric field is constant, the energy flux is never lost and the energy's amplitude varies as 1/r [»feynRP_1963]

Subtopic: electromagnetic waves as independent up

Quote: electromagnetic waves can exist independently of any charges or currents
Quote: if an electrical charge is suddenly moved, its effect is delayed and the electromagnetic field contains the momentum; the sum of field momentum and particle momentum is conserved [»feynRP_1963]
Quote: at a large enough distance, electrical force is proportional to the delayed transverse acceleration divided by the distance
Quote: an electric field moves as a wave outward from the source; i.e., the electromagnetic field is delayed [»feynRP_1963]
Quote: in radiation, the lines of force exist independently of other bodies; may be modified, bounded, propagate over time [»faraM_1855, OK]
Quote: radiation is vibrations of the lines of force; and not the aether [»faraM_1855, OK]
Quote: in radiation, the lines of force exist independently of other bodies; may be modified, bounded, propagate over time [»faraM_1855, OK]
Quote: the atoms of matter are lines of force; the source of radiant phenomena [»faraM_1855, OK]

Subtopic: magnetic field up

Quote: the magnetic field outside a long straight wire is proportional to the current and inversely proportional to the distance from the wire [»feynRP_1964]
Quote: a ring of soft iron can be a strong electromagnetic that retains its force for weeks [»faraM_1855, OK]
Quote: the internal particles of iron are each a magnetic system; as an electromagnetic, they correlate their polarity and combine into a polar whole
Quote: Faraday used lines of magnetic force for quality, direction, and quantity [»faraM_1855, OK]
Quote: are magnetic lines of force the correct abstraction for magnetism [»faraM_1855, OK]
Quote: a line of magnetic force represents a determinate, unchanging, amount of force; no matter how divergent its form [»faraM_1855, OK]
Quote: a line of magnetic force is the line always tangent to a magnetic needle; along which a moving wire does not generate electricity; shown by iron filings [»faraM_1855, OK]
Quote: the continuous, unbounded lines of force represent the nature, condition, direction, and intensity of the magnetic force [»faraM_1855, OK]
Quote: can compress the magnetic lines of force to a small area with other magnets; same total power as the infinite field
[»faraM_1855, OK]

Related Topics up

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Topic: quantum electrodynamics
(34 items)

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