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1

[…] are more likely to be transferred when the plastic rod is rubbed

Electrons (valence electrons - on outer layer)

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2

Identical objects rubber with identical materials […] each other

repel

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3

Electric interactions are [the same as/different from] magnetic interactions

different from

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4

Methods of charging

friction

conduction

induction

grounding

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5

Friction

two neutral objects acquire opposite charge by rubbing against each other

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6

Conduction

charged object directly transfers some excess charge to another object

objects touch → charges move

one object is initially charged

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7

When charges are transferring between objects they [can/cannot] occur in any amount

cannot

electric charge only comes in multiples of e (charge of an electron). charge is quantized, meaning it only occurs in particular amounts

e = -1.6 × 10^-19 C

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8

is 4.0 × 10^-19 C a possible electric charge?

no

divide value by e

2.5 charge transferred, not possible

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9

is -0.00072 C a possible electric charge?

yes

4.5×10^15 charge transferred, possible

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10

Conductor

electrons are not bound and can move freely

can transfer electrons

excess charge resides on outer surface

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11

Non-Conductors

electrons bound to protons and cannot move freely

can only move around proton

cannot transfer electrons

weaker attraction and repulsion than conductors

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12

Induction

a charged object is brought near a neutral object

neutral object becomes charges

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13

Grounding

path for excess charge to flow to ground

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14

Water is a […]

conductor

polar molecule: has positive and negative end

humidity: tiny water molecules in air → act as conductor → distracting electrons by surrounding charged object

people are ~60% water, making them conductors

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15

k =

9×10^9 Nm²/C²

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16

Coulomb’s Law: F_{q }=

k q_{1}q_{2}/r²

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17

Imagine 2 charged balls are hanging from threads. Predict what will happen tot he angle between the strings and the vertical.

Increasing the charge on the balls

increases the angle

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18

Imagine 2 charged balls are hanging from threads. Predict what will happen tot he angle between the strings and the vertical.

Increasing the mass of the balls

decreases the angle

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19

Imagine 2 charged balls are hanging from threads. Predict what will happen tot he angle between the strings and the vertical.

Increasing the string length

decreases the angle

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20

source charge

object that created change in its surrounding space

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21

electric field

change in surrounding space created by source charge; are vectors

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22

test charges

object that interacts with electric field

assume they’re positive and do not have fields

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23

force and field

field allows force to be exerted as distance

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24

E =

F_{q }/q, q - charge in field

k q_{2}/r² , q_{2} - source charge (only for a point charge; one source charge and one test charge)

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25

Electric field (E-field) lines

represents electric field

number of lines is proportional to strength of object’s charge

can never cross or touch other lines

when there is a positively charged object and a negatively charged object, lines start on positively charged object

positive charge: arrows point away from charge

negative charge: arrows point towards charge

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26

uniform electric field

occurs when E-field vectors and E-field lines in a given area are parallel to each other

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27

faraday cage

external electric field causes electric charges in cage (hollow metal box) to be distributed

electrons move from one part of box to another

part where electrons left is now positive

distribution of charges cancel the field’s effect in the cage’s interior

inside, fields cancel out

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28

Electrostatic equilibrium

state reached by charged conductors

when excess charge is placed on a conductor, charges spread out until they reach the lowest energy state possible

there is no net movement of charge

For objects in electrostatic equilibrium…

excess charge migrates to and remains on the outer surface of conductor

there is no electric field inside the conductor (neutral)

the direction of the electric field is perpendicular to the surface of conductor

there is a greater surface charge density at location of higher curvature

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29

Why are you more likely to get shocked when touching a metal object with your finger as opposed to your entire hand?

the finger is smaller and more curved, therefore there is a greater surface charge density

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30

As you increase the potential on an irregularly shaped conductor, a bluish-purple glow called the cornea forms around a sharp end sooner than a smoother end. Why?

As the sharper ends, more curvature → higher charge density

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31

A person rubs a neutral comb through their hair and the comb becomes negatively charged. Why?

The hair loses electrons to the comb.

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32

Consider four charges, A, B, C, and D, which exist in a region of space. Charge A attracts B, but B repels C. Charge C repels D, and D is positively charged. What is the sign of charge A?

A is negatively charged

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33

Two neutral spheres A and B are near each other. A negatively charged rod is brought near one of the spheres as shown. The **far right side** of sphere B is

negative

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34

An electroscope is given a positive charge, causing its foil leaves to separate. When an object is brought near the top plate of the electroscope, the foils separate even further. We could conclude

that the object is positively charged.

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35

According to Coulomb’s law, if the electric force between two charges is positive, the force between the charges is [attractive/repulsive]

The force between the charges is repulsive

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36

What methods of charging result in two oppositely charged objects?

Friction and induction

**friction:**2 neutral objects acquire opposite charges via rubbing (one gains electrons, other loses electrons)**induction:**a charged object is brought near neutral objects, resulting in the separation of charges in the neutral objects

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37

Identify the type of charging: you touch a charged rod to an electroscope

conduction

charged object transfers excess charge to neutral object

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38

Identify the type of charging: you connect a charged object to a much large conductor to neutralize the object

grounding

connecting charged object to larger conductor, which can add or accept excess electrons

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39

Identify the type of charging: you bring a charged object near a neutral soda can. the soda can is attracted to the charged object.

induction

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40

pitch

perception of the frequency of a sound wave

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41

loudness

determined by amplitude of sound wave

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42

open end pipes

ends of harmonics are antinodes

nodes = n

antinode = n+1

wavelength = 2L/n

frequency = nv/2L

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43

closed end pipes

begins with node

nodes = antinodes = n

wavelength = 4L/n

n is odd

frequency = nv/4L

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44

possible harmonics

open end pipes - any number

closed end pipes - odd numbers

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45

fundamental frequency

n =1 (first harmonic)

relationship with overtones: fn = f1 * n

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46

doppler effect

Frequency of sound (pitch) heard by the observer is higher when the observer and source get closer. When observer and source are farther, frequency gets lower

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47

beat frequency

number of "beats" heard per second

fb = f2-f1

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48

beat

two waves completely in phase

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49

standing wave

stationary

remains in constant position

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50

wave sources

amplitude

frequency

type of waves (transversal or longitudinal)

**DO NOT affect speed**

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51

wave medium

density

tension

**affect speed**

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52

traverse wave

disturbance and coil move perpendicular to each other; moves side to side

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53

longitudinal wave

disturbance and coils move parallel to each other

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54

constructive interference

when two pulses meet and they have an amplitude in the same direction → bigger wave

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55

destructive interference

when two pulses meet and they have amplitudes in opposite directions → smaller wave

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56

node (N)

location of minimum/no vibration

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57

antinode (A)

location of max vibration

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58

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60

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62

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63

The SI units for electrical PE are…

joules

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64

What are the accepted symbols for electric potential energy?

U

PE

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65

How would you** increase the electrical potential energy** of a pair of charged particles of the **SAME sign**?

decrease their separation

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66

How would you **decrease the electrical potential energy** of a pair of** OPPOSITELY charged** particles?

decrease their separation

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67

How would you **decrease the electrical potential energy** of a pair of charged particles of the **SAME sign**?

increase their separation

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68

How would you **increase the electrical potential energy** of a pair of** OPPOSITELY charged** particles?

increase their separation

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69

Equation for computing the electrical potential energy stored in a pair of charged particles

K\frac{q1q2}{r}

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70

Electric potential energy is a (scalar/vector) quantity

scalar

It may increase or decrease, but it has no compass direction.

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71

When charged particles are released and can move freely, their electric potential energy will be converted to…

kinetic energy

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72

Units for electric potential

volts

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73

Is electric potential a scalar or vector

scalar

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74

volts in terms of joules/coulombs

1 V = 1 J/C

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75

Electric fields point in the direction that ___ charges freely move when released.

positive

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76

Electric fields point towards locations of ___ potential.

lower

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77

Which way do positively charged particles freely move towards?

direction of lower potential

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78

Which way do negatively charged particles freely move towards?

direction of higher potential

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79

Locations of higher electric potential are _____ positively charged bodies than locations of lower potential

closer to

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80

What are **equipotential surface**s?

locations of the same potential in an electric field

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81

Equipotential surfaces are ___ to electric field vectors

perpendicular

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82

If a location in an electric field has a **potential of 10 V**, it means that **1 coulomb of charge** would ________ at this location

possess 10 J of potential energy

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83

Is potential constant in an uniform electric field?

no

potential changes as you move from one position to another. an electric field is a potential gradient.

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84

If a charged particle moves freely in an electric field, its PE…

decreases

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85

How does the capacitance of a capacitor increase?

increase area (make plates bigger)

decrease r (decrease separation of plates)

use more polar dielectric

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86

The places of capacitors are (insulators/conductors)

conductors

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87

Dielectric is a (insulator/conductor)

insulator

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88

What do capacitors do?

provide a quick burst of energy in automated external defibrillators

provide a quick burst of current in a computer keyboard

maintain a uniform electric field in air purifiers

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89

How would you increased the energy stored in a capacitor?

charge it with a higher voltage battery

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90

Units for capacitance

farads (F)

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91

Equation for finding sum of capacitors in **series**

\frac{1}{Ceq} = \frac{1}{C1} + \frac{1}{C2} + … \frac{1}{Cn}

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92

Equation for finding sum of capacitors in **parallel**

Ceq = C1 + C2 + … Cn

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93

Characteristics of equipotential surfaces/lines/contours

perpendicular to electric field lines

areas where electric potential is the same, regardless of object’s charge

concentric spheres around a single source charge

equipotential contours can never meet or cross

contours are closer = more electric potential energy

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94

test charges seek (higher/lower) energy states

lower

(think of a ball rolling down an incline)

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95

The electric potential energy of interaction of two charged objects is defined to be zero when the **distance **between them is ____

infinitely far away

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96

If two objects have the same sign charges, their electric potential energy is (positive/negative)

positive

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97

If two objects have opposite charges, their electric potential energy is (positive/negative)

negative

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98

If two oppositely charged objects move closer together, their electric potential bar will (increase/decrease) in size

increase

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99

if the Ue between two equal charges quadruples, what happens to the distance between the particles?

distance decreases by a factor of 4 → 1/4

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100

When is the equation ∆Ue = -qEdcosθ used?

when a charge, q, moves freely in an electric field

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