# Shared Flashcard Set

## Details

Electricity and Magnetism:
Terms
55
Physics
Not Applicable
04/09/2009

Term
 Charge (q)
Definition
 entity that defies definition; is measured in units of coulombs (C);
Term
 Coulombs (C)
Definition
 unit of measurement used to quantitatively describe a charge
Term
 Universal Law of Conservation of Charge
Definition
 The universe has no net charge; net charge is created by separating electrons from protons.
Term
 Electron unit (e)
Definition
 smallest unit of charge; e = 1.6x10^-19 C
Term
 Attraction of charges
Definition
 Opp. charges attract each other; like charges repel each other.
Term
 Coulomb's Law
Definition
 Describes the magnitude of repulsive/attractive forces between two charged objects; F = k(q1q2/r^2)
Term
 Center of charge
Definition
 originating point on an object from which a charge is generated
Term
 Field
Definition
 man-made concept designed to explain action at a distance
Term
 Lines of force (Lof)
Definition
 used to represent fields; lof point in the direction of the field (e fields: + --> -; g fields: --> mass creating the field)
Term
 Electric field (E)
Definition
 electrostatic force per unit charge; units are given as N/C or V/m.
Term
 Eqtn for electric field of a point charge
Definition
 E = k(q1/r^2)
Term
 Eqtn for force (F) on a charge (q) in an electric field (E)
Definition
 F = Eq
Term
 Eqtn for potential energy (U) of a charge in an electric field
Definition
 U = Eqd (notice similarity to gravitational PE - U = mgh)
Term
 Voltage (V)
Definition
 the potential for work by an electric field in moving any charge from one point to another; V = Ed; units = volts (V) - J/C
Term
 Volts (V)
Definition
 unit of measurement used to define voltage; can be expressed as J/C
Term
 Eqtn for voltage due to a point charge
Definition
 V = k(q1/r)
Term
 Equipotential surfaces
Definition
 surfaces normal to an electric field that describe a set of points all with the same potential (V)
Term
 Electric dipole
Definition
 created by two opp. charges with equal magnitude
Term
 Electric dipole moment (p = qd)
Definition
 a vector whose magnitude is the charge q on one of the charges times the distance between the charges
Term
 Review of eqtns for an electric field created by a point charge
Definition
 Eqtn UnitsF = k(q1q2/r^2) NE = k(q1/r^2) N/C or V/mU = k(q1q2/r) JV = k(q1/r)
Term
 Conductors
Definition
 allow e's to flow relatively freely (i.e. metals)
Term
 Resistors
Definition
 (poor conductors) hold e's tightly in place and impede free flow of e's (i.e. network solids such as diamonds and glass)
Term
 Induction
Definition
 method of charging a conductor by moving -ly charged objects close to electrically insulated conductors
Term
 Current
Definition
 flow of moving charges; given in amps (A) or C/s
Term
 Amps (A)
Definition
 unit of measurement used to describe current; also given as C/s
Term
 Circuit
Definition
 cyclical pathway for moving charge
Term
 Resistivity (p - rho)
Definition
 quantitative measure of a substance's resistance to flow of charge
Term
 Resistance (R)
Definition
 quantitative measure of an object of a particular shape and size to resist the flow of charge; measured in ohms
Term
 Ohm
Definition
 measurement used to describe an object's resistance
Term
 Eqtn for a material's resistivity
Definition
 R = p(rho)x(L/A); where L = length and A = area
Term
 Ohm's Law
Definition
 eqtn that relates voltage (V), current (i), and resistance (R: V = iR
Term
 Kirchoff's first rule
Definition
 the amount of current flowing into any node (intersection of wires) must be the same amount that flows out
Term
 Kirchoff's second rule
Definition
 the voltage around any path in a circuit must sum to 0
Term
 Electromotive force (EMF)
Definition
 means of rating batteries; not a true force, simply a fancy word for voltage
Term
 Capacitor
Definition
 used to temporarily store energy in a circuit; E is stored in the form of separated charge
Term
 Parallel plate capacitor
Definition
 two plates, made from conductive material, that are separated by a very small distance; on a charged capacitor: one plate holds + charge while the other wholes the same amount of - charge
Term
 Capacitance
Definition
 ability to store charge per unit voltage; C = Q/V
Term
 Eqtns for the energy (U) stored in any shape capacitor
Definition
 U = 1/2QV or (others derived from C = Q/V)U = 1/2CV^2 or U = 1/2Q^2/C
Term
 Dielectric constant (K)
Definition
 refers to substance between the plates of a capacitor (must be an insulator); resists the creation of an electric field, thus allowing the capacitor to store more energy
Term
 Relation between voltage and time as defined by batteries (charging/discharging)
Definition
 Charging: V increases with timeDischarging: V decreases with time
Term
 Eqtns for resistance and capacitance in circuits (series & parallel)
Definition
 Resistance: eff = TotalReff = R1 + R2 +... (series)1/Reff = 1/R1 + 1/R2 +... (parallel)Capacitance:Ceff = C1 + C2 +... (parallel)1/Ceff = 1/C1 + 1/C2 +... (series)
Term
 Power
Definition
 rate of energy transfer; electrical power eqtns: P = iV; P = i^2R; P = V^2/R
Term
 Power
Definition
 Concept often used to integrate electricity and mechanics into the same question
Term
 Power dissipated
Definition
 rate at which heat is generated as current goes through a resistor
Term
 Direct current (DC current)
Definition
 net movement of e's is in one direction around a circuit
Term
 Alternating current (AC current)
Definition
 created by oscillating e's back and forth in SHM; commonly used in home outlets in the U.S.
Term
 Voltage and Current for AC current
Definition
 described as sine waves; max current occurs at max velocity; eqtns:Vmax = sqrt2xVrms; imax = sqrt2xirms
Term
 Tesla (T)
Definition
 unit of measurement used to describe magnetic field strenth
Term
 Changing electric fields create magnetic fields; stationary charges do not create magnetic fields
Definition
Term
 Force (experienced by a charge moving through a magnetic field)
Definition
 Force (F) on a charge (q) moving with velocity (v) through a magnetic field (B) is:F = qvBsin(theta)
Term
 Force (experienced by a charge moving through a magnetic field)
Definition
 Force (F) on a charge (q) moving with velocity (v) through a magnetic field (B) is:F = qvBsin(theta)theta = angle b/t mag field and charge velocity
Term
 Direction of force (experienced by a charge moving through a magnetic field)
Definition
 the force is directed perpendicularly to both velocity and the mag. field
Term
 Changing magnetic fields create electric fields
Definition
Term
 Describe the source and flow of energy in situations in which electrical fields are induced
Definition
 Mechanical E is transferred to internal E because the forces due to induced e fields are non-conservative
Term
 Moving charges, magnetic fields, and forces
Definition
 A moving charge generates a mag field; when moving through a mag field, a moving charge experiences force
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