Particle properties {charge, electricity}| can cause electric force. Electron charge {negative charge} is one negative unit. Proton charge {positive charge} is one positive unit. Total electric charge is sum of particle electric charges.
static electricity
Rubbing glass with cloth keeps protons on glass and puts electrons on cloth. Rubbing rubber with cloth puts electrons on rubber and keeps protons on cloth. Rubbing energy frees electrons from rubbed material surface. Quickly pulling the materials apart leaves net charge on both materials. Sliding on rugs rubs electrons off rug, and touching metal doorknobs makes electrons jump to metal.
static electricity: lightning
High winds, when hot air rises, rub higher cold air, separate electrons from air molecules, and take electrons away before they can recombine. Lightning carries electrons back to positive-charge regions or to ground.
strong nuclear force
Only strong nuclear force can change particle electric charge.
Surface voltages can move charges around semiconductors {charge coupling}|. Semiconductors have capacitance. Charge moves between capacitors at each clock pulse. Solid-state TV cameras and memory circuits use charge coupling. Semiconductors {charge coupled device} (CCD) can move free electric charges from one storage element to another, by externally changing voltage. Charge can vary by varying voltage and capacitance. Image sensors and computer memories use CCDs.
Electric forces on materials can pull electrons in one direction and protons in opposite direction {induction, charge} {charge induction}|.
dielectric
Conductors have free charges, so charges move to counter outside electric force, with no net charge. Dielectrics have no free charges, so induction pulls electrons and protons apart to make induced charge and dipoles.
factors
If electric field is more, electric force is more, and system has more dipoles. If atoms are small, smaller mass moves easier, and system has more dipoles.
factors: temperature
In polar materials, if temperature is lower, material has fewer random motions, and material has more dipoles. In non-polar materials, temperature has little effect.
factors: frequency
If electric-field frequency is more than 10^10 Hz, dipole moments cancel, because dipole moments change slower than field changes. If electric-field frequency is above 10^11 Hz, bending and stretching dipole moments cancel, because vibrations are slower than frequency, and only electrons affect polarization.
examples
Sifting sugar or streaming water through electric fields illustrates charge induction.
Outside electric force on dielectrics can pull electrons one way and protons opposite way, to separate charges {dipole}|. Negative charges are at one end, and positive charges are at other end, along outside-electric-field direction.
Instruments {electroscope}| can detect static electricity.
Friction can cause glow {St. Elmo's fire}| around objects in storms.
Objects can have stationary extra surface charges {static electricity}|. Electric charge is on material surface, because electrons repel each other to farthest points. More charges are at higher-curvature surface points, because repulsions are less where average distances are more. Sparks, van de Graaf generators, pith balls, cloths and rods, and electroscopes demonstrate static electricity.
Ions can have charge {valence, ion}, of -7 to +7.
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Date Modified: 2022.0225