Class Four

Question 1

value of elementary charge

Answer 1

e = 1.6 x 10^-19 C

Question 2

what does it mean when charge is quantized

Answer 2

charge on an object can only be a whole number of e’s

Question 3

charge is quantized formula

Answer 3

q = n (+/- e)

Question 4

Coulomb’s law

Answer 4

Question 5

Coulomb’s constant

Answer 5

9 x 10⁹ N.m²/C²

Question 6

principle of superposition

Answer 6

adding the resulting forces

Question 7

source charges

Answer 7

the charges that create an electric field

Question 8

electric field formula

Answer 8

E = k(Q/r²)

Question 9

electric force & field formula

Answer 9

F = qE

Question 10

conductors

Answer 10

contains charges that are free to roam throughout material

Question 11

most important conductors

Answer 11

metals

Question 12

insulators

Answer 12

don’t have free charges → electrons are tightly bound to their atoms

Question 13

if an object moves with nature..

Answer 13

its potential energy decreases

Question 14

if an object moves against nature..

Answer 14

its potential energy increases

Question 15

electric potential formula

Answer 15

= k (Q/r)

Question 16

positive charges want to move to regions of..

Answer 16

lower potential

Question 17

negative charges want to move to regions of..

Answer 17

higher potential

Question 18

what causes a net movement of charge

Answer 18

electrons’ drift velocity

Question 19

current formula

Answer 19

I = Q / time

Question 20

what is current

Answer 20

charge over time

Question 21

what creates a current

Answer 21

voltage

Question 22

resistance formula

Answer 22

R = V / I

voltage / resulting current

Question 23

resistance and resistivity formula

Answer 23

R = p (L/A)

p = intrinsic resistivity

L = length

A = area

Question 24

Ohm’s law

Answer 24

V = IR

voltage = current x resistance

Question 25

what is a resistor

Answer 25

component in an electric circuit that has a specific + known resistance

Question 26

when are resistors in series

Answer 26

if they follow eachother along a single connection in a circuit

Question 27

when are resistors in parallel

Answer 27

when they provide alternative routes from one point in a circuit to another

Question 28

how do we combine resistors in series

Answer 28

we add them together

Question 29

how do we combine resistors in parallel

Answer 29

take the product of the resistors and then divide it by the sum R1R2 / R1 + R2

Question 30

job of a voltage source

Answer 30

maintain a potential difference between terminals

Question 31

positive terminal

Answer 31

longer line → higher potential

Question 32

negative terminal

Answer 32

shorter line → lower potential

Question 33

resistors in series always share the same..

Answer 33

current

Question 34

resistors in parallel always share the same..

Answer 34

voltage

Question 35

Kirchhoff's law

Answer 35

at a junction in an electrical circuit, the sum of currents flowing into the junction is equal to the sum of currents flowing out of the junction

Question 36

power dissipated by a resistor: joule heating law

Answer 36

P = I²R

Question 37

what do voltmeters do

Answer 37

measure the potential differences between 2 points in a circuit

Question 38

what do ammeters do

Answer 38

measure the current through a particular point in the circuit

Question 39

what is a capacitor

Answer 39

a pair of conductors that can hold equal but opposite charges

Question 40

charge on a capacitor formula

Answer 40

Q = CV charge on capacitor = proportionality constant x potential diff between the plates

Question 41

what is capacitance dependent on

Answer 41

sizes of the plates and how far apart they are

Question 42

capacitance formula

Answer 42

C = e (A/d) e = permittivity of free space (constant) A = area d = diameter

Question 43

2 purposes of a parallel plate capacitor

Answer 43

create a uniform electric field store electrical potential energy

Question 44

Ed's formula

Answer 44

V = Ed used with parallel plate capacitor

Question 45

feature of a parallel plate capacitor

Answer 45

electric field is the same magnitude at every point between the plates

Question 46

electrical PE stored in a capacitor formula

Answer 46

PE = ½QV

Question 47

what are dielectrics

Answer 47

insulating material that goes in-between capacitance plates

Question 48

purpose of dielectrics (2)

Answer 48

keeps plates from touching increases capacitance

Question 49

what happens when you disconnect the battery and insert dielectric (4)

Answer 49

C increases by a factor of K Q stays the same V decreases by a factor of K E decreases by a factor of K

Question 50

what happens when you keep the battery connected and insert dielectric (4)

Answer 50

C increases by a factor of K Q increases by a factor of K V and E stays the same

Question 51

if charge is held constant and capacitance increases,

Answer 51

PE decreases

Question 52

sif voltage is held constant and capacitance increases..

Answer 52

PE increases