CH. 21 ELECTRIC FIELD I: DISCRETE CHARGE DISTRIBUTIONS

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Physics Fichas sobre CH. 21 ELECTRIC FIELD I: DISCRETE CHARGE DISTRIBUTIONS, creado por Veronica Martinez el 22/11/2016.
Veronica Martinez
Fichas por Veronica Martinez, actualizado hace más de 1 año
Veronica Martinez
Creado por Veronica Martinez hace alrededor de 8 años
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Pregunta Respuesta
ELECTRIC CHARGE -Fundamental property of matter. -Many particles including the electron and proton carry it. -Comes in two varieties, positive and negative. -Most charged particles carry exactly one elementary charge, e, either positive or negative. -In a closed system is conserved, the algebraic sum of charges remains unchanged. [True even if new particles are created or destroyed.] -SI unit is coulomb (C), equal to approx 6.25 e 18 elementary charges.
Plastic Rods
Glass Rod
Proton Carries exactly +e
Electron Carries exactly -e
e 1.6x10^(-19)C
Atom Most of the volume is occupied sparsely by electrons. Electrons move, protons don't.
Atomic Charge Protons and electrons account for it.
Nucleus Tiny compares with rest of the atom, contains over 99.9% of the atom's mass.
Positive Net Charge Fewer electrons than protons.
Negative Net Charge More electrons than protons.
Charging by Induction (steps) 1. Uncharged metal ball 2. Neg. charge on rod repels electrons, creating zones of negative and positive induced charge. 3. Wire lets electron build-up (induced neg. charge) flow into ground. 4. Wire removed: ball now has an electron deficient region of positive charge. 5. Rod removed; pos. charge spreads over ball
Charging by Induction (definition) The process in which a charged object can give another object a charge of opposite sign without losing any of its own charge is called induction.
Electric Force -Makes like charges repel, and opposite charges attract. -Depends on the product of the two charges and inverse square of the distance between them. -Mathematically, described by Coulomb's law.
Coulomb's Law 1/2
Coulomb's Law 2/2
Superposition Principle -Means the force two charges exert on a third force is just the vector sum of the forces from the two charges, each treated without regard to the other charge. -Obeyed by the electric force.
Electric Field -At a point in space is the force per unit charge q placed at that point would experience: E=F/q -The force on a charge q in an electric field E is F=qE -Field lines always point away from + charges and toward - charges. -At each point in space, the electric field vector is tangent to the field line passing through that point.
Field Lines for Simple Charge Distributions
Fields of Point Charges Radial, outward for a positive charge and inward for negative charge. E=kq/(r^2)
Charge Distributions Superposition principle shows that the field due to a charge distribution is the vector sum of the fields of the individual charges.
Electric Dipole IMPORTANT Charge Distribution -Consists of two point charges of equal magnitude but opposite signs, held a shor distance apart. -Electrically neutral, but the separation of its charges results in an electric field. -Many charge distributions, especially molecules, behave like electric dipoles. -The product of the charge separation is the dipole moment: p=qd -Far from the dipole, its electric field falls off as the inverse cube of the distance.
Conductors Materials in which charge is free to move.
Insulators -Materials in which charge isn't free to move. -Alignment of molecular dipoles reduces an externally applied field.
Dielectrics -Materials generally contain molecular dipoles, which experience torques and forces in electric fields.
Induced Dipole Moments Even if molecules aren't intrinsically dipoles, the acquire IDM as a result of electric forces stretching the molecule.
Motion of Point Charges in Electric Fields When a particle that has a charge q is placed in an electric field E, it experiences a force qE. If the electric force is the only force acting on the particle, the particle has acceleration.
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