Ch 15-17

Question 1

Insulator

Answer 1

electrons tightly held by the nucleus; held by covalent bonds; right side on periodic table

Question 2

Conductor

Answer 2

electrons loosely held by nucleus; metallic left side of periodic table; really want to give up e-; typically 1 e-per atom free

Question 3

Induction

Answer 3

inducing a charge separation in a neutral substance ; only works with attraction;

Question 4

Static Electricity

Answer 4

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

Question 5

Lightening

Answer 5

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

Question 6

Superposition

Answer 6

the total F is the vector sum of the individual forces; LIKELY TO BE ON THE EXAM

Question 7

Electric Field

Answer 7

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

Question 8

Conductor Properties

Answer 8

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

Question 9

Electric Flux

Answer 9

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

Question 10

Millikan Oil Drop Experiment

Answer 10

you can balance mg and E-field so some of the oil drops freeze/float; charge was quantized this way in units of e-

Question 11

Van de Graaf

Answer 11

rubber steals/drops off charges when it reaches the metal; these excess charges go to the outside of a metal (best in dry conditions)

Question 12

Gauss’s Law

Answer 12

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

Question 13

Potential for a point charge

Answer 13

k (q/r); or Ed

Question 14

Relationship between work and PE

Answer 14

w= -PE;

Question 15

Work for Electricity

Answer 15

W= Fd = qEd

Question 16

Sign conventions of Potential

Answer 16

+ charges lead to + potential
- charges lead to -potential
moving towards + charges gives + V
assumes V= 0 at r = infinity

Question 17

Equipotential Surfaces

Answer 17

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;

Question 18

Capacitor

Answer 18

capacity to hold charge; a device used for rapid release of electronic units; stores energy to be reclaimed;

Question 19

Capacitance

Answer 19

C =Q/∆V

Question 20

Parallel Plate Capacitor Capacitance

Answer 20

C= e A/d

Question 21

Capacitors in Parallel

Answer 21

C = C1 + C2 + …

Question 22

Capacitors in Series

Answer 22

1/C = 1/C1 + 1/C2 + …

Question 23

Energy Stored in a Charged Capacitor

Answer 23

U = 1/2Q∆V = 1/2C(∆V)^2 = Q^2/2C

Question 24

Dielectric

Answer 24

an insulating material that increases capacitance, decreases voltage, decreases E-field, and either increases or decreases energy stored

Question 25

Capacitance with a Dielectric

Answer 25

multiply capacitance by the dielectric constant k

Question 26

Current

Answer 26

the rate at which charge flows through this surface; represented by I

Question 27

Current Density

Answer 27

current/area or sigmaE; also equal to E-field/resistivity

Question 28

Temperature and Resistance for conductors

Answer 28

as temperature rises, resistance increases due to the molecules moving quicker

Question 29

Temperature and Resistance of Semiconductors

Answer 29

As temperature increases, resistance decreases because it frees more electrons

Question 30

Temperature and Resistance of Superconductors

Answer 30

At a certain Temperature, resistance drops to 0

Question 31

Resistivity

Answer 31

represented by roe;

Question 32

Resistance

Answer 32

roe times length over area