Ch 15-17 Flashcards
(32 cards)
Insulator
electrons tightly held by the nucleus; held by covalent bonds; right side on periodic table
Conductor
electrons loosely held by nucleus; metallic left side of periodic table; really want to give up e-; typically 1 e-per atom free
Induction
inducing a charge separation in a neutral substance ; only works with attraction;
Static Electricity
friction between two objects will lead to one stealing e-s from another, and they become charged; then these extra e-s leap to be grounded at a metal door knob
Lightening
unstable air with huge updraft as a bottom part of a cloud gets charged negatively, and causes the positive charges to be drawn towards the cloud; this can cause lightening if electron attraction is strong enough
Superposition
the total F is the vector sum of the individual forces; LIKELY TO BE ON THE EXAM
Electric Field
exists in the region of space around a charged object; the force is exerted by something (the field) that is in the same location as the charged object; depends only on the charge q and the distance r from that object to a point in space
Conductor Properties
electric field is zero everywhere inside the material; any excess charge resides on the surface; E-field is perpendicular to the conductor’s surface; and the charge accumulates at sharp points
Electric Flux
a measure of how much the E-field vectors penetrated a given surface; flux lines passing into the interior of the volume are negative and those passing out of the interior are positive
Millikan Oil Drop Experiment
you can balance mg and E-field so some of the oil drops freeze/float; charge was quantized this way in units of e-
Van de Graaf
rubber steals/drops off charges when it reaches the metal; these excess charges go to the outside of a metal (best in dry conditions)
Gauss’s Law
the total electric flux leaving a closed surface is equal to the charge; can be used to find an E-field; works for symmetrical surfaces when the charge is enclosed
Potential for a point charge
k (q/r); or Ed
Relationship between work and PE
w= -PE;
Work for Electricity
W= Fd = qEd
Sign conventions of Potential
+ charges lead to + potential
- charges lead to -potential
moving towards + charges gives + V
assumes V= 0 at r = infinity
Equipotential Surfaces
potential in a conductor is constant; no work is required to move a charge at constant speed; the electric field is perpendicular to the surface;
Capacitor
capacity to hold charge; a device used for rapid release of electronic units; stores energy to be reclaimed;
Capacitance
C =Q/∆V
Parallel Plate Capacitor Capacitance
C= e A/d
Capacitors in Parallel
C = C1 + C2 + …
Capacitors in Series
1/C = 1/C1 + 1/C2 + …
Energy Stored in a Charged Capacitor
U = 1/2Q∆V = 1/2C(∆V)^2 = Q^2/2C
Dielectric
an insulating material that increases capacitance, decreases voltage, decreases E-field, and either increases or decreases energy stored
