671 lines
53 KiB
HTML
671 lines
53 KiB
HTML
<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/><title>Unit 21: Coulomb’s Law</title><style>
|
||
/* cspell:disable-file */
|
||
/* webkit printing magic: print all background colors */
|
||
html {
|
||
-webkit-print-color-adjust: exact;
|
||
}
|
||
* {
|
||
box-sizing: border-box;
|
||
-webkit-print-color-adjust: exact;
|
||
}
|
||
|
||
html,
|
||
body {
|
||
margin: 0;
|
||
padding: 0;
|
||
}
|
||
@media only screen {
|
||
body {
|
||
margin: 2em auto;
|
||
max-width: 900px;
|
||
color: rgb(55, 53, 47);
|
||
}
|
||
}
|
||
|
||
body {
|
||
line-height: 1.5;
|
||
white-space: pre-wrap;
|
||
}
|
||
|
||
a,
|
||
a.visited {
|
||
color: inherit;
|
||
text-decoration: underline;
|
||
}
|
||
|
||
.pdf-relative-link-path {
|
||
font-size: 80%;
|
||
color: #444;
|
||
}
|
||
|
||
h1,
|
||
h2,
|
||
h3 {
|
||
letter-spacing: -0.01em;
|
||
line-height: 1.2;
|
||
font-weight: 600;
|
||
margin-bottom: 0;
|
||
}
|
||
|
||
.page-title {
|
||
font-size: 2.5rem;
|
||
font-weight: 700;
|
||
margin-top: 0;
|
||
margin-bottom: 0.75em;
|
||
}
|
||
|
||
h1 {
|
||
font-size: 1.875rem;
|
||
margin-top: 1.875rem;
|
||
}
|
||
|
||
h2 {
|
||
font-size: 1.5rem;
|
||
margin-top: 1.5rem;
|
||
}
|
||
|
||
h3 {
|
||
font-size: 1.25rem;
|
||
margin-top: 1.25rem;
|
||
}
|
||
|
||
.source {
|
||
border: 1px solid #ddd;
|
||
border-radius: 3px;
|
||
padding: 1.5em;
|
||
word-break: break-all;
|
||
}
|
||
|
||
.callout {
|
||
border-radius: 3px;
|
||
padding: 1rem;
|
||
}
|
||
|
||
figure {
|
||
margin: 1.25em 0;
|
||
page-break-inside: avoid;
|
||
}
|
||
|
||
figcaption {
|
||
opacity: 0.5;
|
||
font-size: 85%;
|
||
margin-top: 0.5em;
|
||
}
|
||
|
||
mark {
|
||
background-color: transparent;
|
||
}
|
||
|
||
.indented {
|
||
padding-left: 1.5em;
|
||
}
|
||
|
||
hr {
|
||
background: transparent;
|
||
display: block;
|
||
width: 100%;
|
||
height: 1px;
|
||
visibility: visible;
|
||
border: none;
|
||
border-bottom: 1px solid rgba(55, 53, 47, 0.09);
|
||
}
|
||
|
||
img {
|
||
max-width: 100%;
|
||
}
|
||
|
||
@media only print {
|
||
img {
|
||
max-height: 100vh;
|
||
object-fit: contain;
|
||
}
|
||
}
|
||
|
||
@page {
|
||
margin: 1in;
|
||
}
|
||
|
||
.collection-content {
|
||
font-size: 0.875rem;
|
||
}
|
||
|
||
.column-list {
|
||
display: flex;
|
||
justify-content: space-between;
|
||
}
|
||
|
||
.column {
|
||
padding: 0 1em;
|
||
}
|
||
|
||
.column:first-child {
|
||
padding-left: 0;
|
||
}
|
||
|
||
.column:last-child {
|
||
padding-right: 0;
|
||
}
|
||
|
||
.table_of_contents-item {
|
||
display: block;
|
||
font-size: 0.875rem;
|
||
line-height: 1.3;
|
||
padding: 0.125rem;
|
||
}
|
||
|
||
.table_of_contents-indent-1 {
|
||
margin-left: 1.5rem;
|
||
}
|
||
|
||
.table_of_contents-indent-2 {
|
||
margin-left: 3rem;
|
||
}
|
||
|
||
.table_of_contents-indent-3 {
|
||
margin-left: 4.5rem;
|
||
}
|
||
|
||
.table_of_contents-link {
|
||
text-decoration: none;
|
||
opacity: 0.7;
|
||
border-bottom: 1px solid rgba(55, 53, 47, 0.18);
|
||
}
|
||
|
||
table,
|
||
th,
|
||
td {
|
||
border: 1px solid rgba(55, 53, 47, 0.09);
|
||
border-collapse: collapse;
|
||
}
|
||
|
||
table {
|
||
border-left: none;
|
||
border-right: none;
|
||
}
|
||
|
||
th,
|
||
td {
|
||
font-weight: normal;
|
||
padding: 0.25em 0.5em;
|
||
line-height: 1.5;
|
||
min-height: 1.5em;
|
||
text-align: left;
|
||
}
|
||
|
||
th {
|
||
color: rgba(55, 53, 47, 0.6);
|
||
}
|
||
|
||
ol,
|
||
ul {
|
||
margin: 0;
|
||
margin-block-start: 0.6em;
|
||
margin-block-end: 0.6em;
|
||
}
|
||
|
||
li > ol:first-child,
|
||
li > ul:first-child {
|
||
margin-block-start: 0.6em;
|
||
}
|
||
|
||
ul > li {
|
||
list-style: disc;
|
||
}
|
||
|
||
ul.to-do-list {
|
||
text-indent: -1.7em;
|
||
}
|
||
|
||
ul.to-do-list > li {
|
||
list-style: none;
|
||
}
|
||
|
||
.to-do-children-checked {
|
||
text-decoration: line-through;
|
||
opacity: 0.375;
|
||
}
|
||
|
||
ul.toggle > li {
|
||
list-style: none;
|
||
}
|
||
|
||
ul {
|
||
padding-inline-start: 1.7em;
|
||
}
|
||
|
||
ul > li {
|
||
padding-left: 0.1em;
|
||
}
|
||
|
||
ol {
|
||
padding-inline-start: 1.6em;
|
||
}
|
||
|
||
ol > li {
|
||
padding-left: 0.2em;
|
||
}
|
||
|
||
.mono ol {
|
||
padding-inline-start: 2em;
|
||
}
|
||
|
||
.mono ol > li {
|
||
text-indent: -0.4em;
|
||
}
|
||
|
||
.toggle {
|
||
padding-inline-start: 0em;
|
||
list-style-type: none;
|
||
}
|
||
|
||
/* Indent toggle children */
|
||
.toggle > li > details {
|
||
padding-left: 1.7em;
|
||
}
|
||
|
||
.toggle > li > details > summary {
|
||
margin-left: -1.1em;
|
||
}
|
||
|
||
.selected-value {
|
||
display: inline-block;
|
||
padding: 0 0.5em;
|
||
background: rgba(206, 205, 202, 0.5);
|
||
border-radius: 3px;
|
||
margin-right: 0.5em;
|
||
margin-top: 0.3em;
|
||
margin-bottom: 0.3em;
|
||
white-space: nowrap;
|
||
}
|
||
|
||
.collection-title {
|
||
display: inline-block;
|
||
margin-right: 1em;
|
||
}
|
||
|
||
.simple-table {
|
||
margin-top: 1em;
|
||
font-size: 0.875rem;
|
||
empty-cells: show;
|
||
}
|
||
.simple-table td {
|
||
height: 29px;
|
||
min-width: 120px;
|
||
}
|
||
|
||
.simple-table th {
|
||
height: 29px;
|
||
min-width: 120px;
|
||
}
|
||
|
||
.simple-table-header-color {
|
||
background: rgb(247, 246, 243);
|
||
color: black;
|
||
}
|
||
.simple-table-header {
|
||
font-weight: 500;
|
||
}
|
||
|
||
time {
|
||
opacity: 0.5;
|
||
}
|
||
|
||
.icon {
|
||
display: inline-block;
|
||
max-width: 1.2em;
|
||
max-height: 1.2em;
|
||
text-decoration: none;
|
||
vertical-align: text-bottom;
|
||
margin-right: 0.5em;
|
||
}
|
||
|
||
img.icon {
|
||
border-radius: 3px;
|
||
}
|
||
|
||
.user-icon {
|
||
width: 1.5em;
|
||
height: 1.5em;
|
||
border-radius: 100%;
|
||
margin-right: 0.5rem;
|
||
}
|
||
|
||
.user-icon-inner {
|
||
font-size: 0.8em;
|
||
}
|
||
|
||
.text-icon {
|
||
border: 1px solid #000;
|
||
text-align: center;
|
||
}
|
||
|
||
.page-cover-image {
|
||
display: block;
|
||
object-fit: cover;
|
||
width: 100%;
|
||
max-height: 30vh;
|
||
}
|
||
|
||
.page-header-icon {
|
||
font-size: 3rem;
|
||
margin-bottom: 1rem;
|
||
}
|
||
|
||
.page-header-icon-with-cover {
|
||
margin-top: -0.72em;
|
||
margin-left: 0.07em;
|
||
}
|
||
|
||
.page-header-icon img {
|
||
border-radius: 3px;
|
||
}
|
||
|
||
.link-to-page {
|
||
margin: 1em 0;
|
||
padding: 0;
|
||
border: none;
|
||
font-weight: 500;
|
||
}
|
||
|
||
p > .user {
|
||
opacity: 0.5;
|
||
}
|
||
|
||
td > .user,
|
||
td > time {
|
||
white-space: nowrap;
|
||
}
|
||
|
||
input[type="checkbox"] {
|
||
transform: scale(1.5);
|
||
margin-right: 0.6em;
|
||
vertical-align: middle;
|
||
}
|
||
|
||
p {
|
||
margin-top: 0.5em;
|
||
margin-bottom: 0.5em;
|
||
}
|
||
|
||
.image {
|
||
border: none;
|
||
margin: 1.5em 0;
|
||
padding: 0;
|
||
border-radius: 0;
|
||
text-align: center;
|
||
}
|
||
|
||
.code,
|
||
code {
|
||
background: rgba(135, 131, 120, 0.15);
|
||
border-radius: 3px;
|
||
padding: 0.2em 0.4em;
|
||
border-radius: 3px;
|
||
font-size: 85%;
|
||
tab-size: 2;
|
||
}
|
||
|
||
code {
|
||
color: #eb5757;
|
||
}
|
||
|
||
.code {
|
||
padding: 1.5em 1em;
|
||
}
|
||
|
||
.code-wrap {
|
||
white-space: pre-wrap;
|
||
word-break: break-all;
|
||
}
|
||
|
||
.code > code {
|
||
background: none;
|
||
padding: 0;
|
||
font-size: 100%;
|
||
color: inherit;
|
||
}
|
||
|
||
blockquote {
|
||
font-size: 1.25em;
|
||
margin: 1em 0;
|
||
padding-left: 1em;
|
||
border-left: 3px solid rgb(55, 53, 47);
|
||
}
|
||
|
||
.bookmark {
|
||
text-decoration: none;
|
||
max-height: 8em;
|
||
padding: 0;
|
||
display: flex;
|
||
width: 100%;
|
||
align-items: stretch;
|
||
}
|
||
|
||
.bookmark-title {
|
||
font-size: 0.85em;
|
||
overflow: hidden;
|
||
text-overflow: ellipsis;
|
||
height: 1.75em;
|
||
white-space: nowrap;
|
||
}
|
||
|
||
.bookmark-text {
|
||
display: flex;
|
||
flex-direction: column;
|
||
}
|
||
|
||
.bookmark-info {
|
||
flex: 4 1 180px;
|
||
padding: 12px 14px 14px;
|
||
display: flex;
|
||
flex-direction: column;
|
||
justify-content: space-between;
|
||
}
|
||
|
||
.bookmark-image {
|
||
width: 33%;
|
||
flex: 1 1 180px;
|
||
display: block;
|
||
position: relative;
|
||
object-fit: cover;
|
||
border-radius: 1px;
|
||
}
|
||
|
||
.bookmark-description {
|
||
color: rgba(55, 53, 47, 0.6);
|
||
font-size: 0.75em;
|
||
overflow: hidden;
|
||
max-height: 4.5em;
|
||
word-break: break-word;
|
||
}
|
||
|
||
.bookmark-href {
|
||
font-size: 0.75em;
|
||
margin-top: 0.25em;
|
||
}
|
||
|
||
.sans { font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol"; }
|
||
.code { font-family: "SFMono-Regular", Menlo, Consolas, "PT Mono", "Liberation Mono", Courier, monospace; }
|
||
.serif { font-family: Lyon-Text, Georgia, ui-serif, serif; }
|
||
.mono { font-family: iawriter-mono, Nitti, Menlo, Courier, monospace; }
|
||
.pdf .sans { font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol", 'Twemoji', 'Noto Color Emoji', 'Noto Sans CJK JP'; }
|
||
.pdf:lang(zh-CN) .sans { font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol", 'Twemoji', 'Noto Color Emoji', 'Noto Sans CJK SC'; }
|
||
.pdf:lang(zh-TW) .sans { font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol", 'Twemoji', 'Noto Color Emoji', 'Noto Sans CJK TC'; }
|
||
.pdf:lang(ko-KR) .sans { font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol", 'Twemoji', 'Noto Color Emoji', 'Noto Sans CJK KR'; }
|
||
.pdf .code { font-family: Source Code Pro, "SFMono-Regular", Menlo, Consolas, "PT Mono", "Liberation Mono", Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK JP'; }
|
||
.pdf:lang(zh-CN) .code { font-family: Source Code Pro, "SFMono-Regular", Menlo, Consolas, "PT Mono", "Liberation Mono", Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK SC'; }
|
||
.pdf:lang(zh-TW) .code { font-family: Source Code Pro, "SFMono-Regular", Menlo, Consolas, "PT Mono", "Liberation Mono", Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK TC'; }
|
||
.pdf:lang(ko-KR) .code { font-family: Source Code Pro, "SFMono-Regular", Menlo, Consolas, "PT Mono", "Liberation Mono", Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK KR'; }
|
||
.pdf .serif { font-family: PT Serif, Lyon-Text, Georgia, ui-serif, serif, 'Twemoji', 'Noto Color Emoji', 'Noto Serif CJK JP'; }
|
||
.pdf:lang(zh-CN) .serif { font-family: PT Serif, Lyon-Text, Georgia, ui-serif, serif, 'Twemoji', 'Noto Color Emoji', 'Noto Serif CJK SC'; }
|
||
.pdf:lang(zh-TW) .serif { font-family: PT Serif, Lyon-Text, Georgia, ui-serif, serif, 'Twemoji', 'Noto Color Emoji', 'Noto Serif CJK TC'; }
|
||
.pdf:lang(ko-KR) .serif { font-family: PT Serif, Lyon-Text, Georgia, ui-serif, serif, 'Twemoji', 'Noto Color Emoji', 'Noto Serif CJK KR'; }
|
||
.pdf .mono { font-family: PT Mono, iawriter-mono, Nitti, Menlo, Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK JP'; }
|
||
.pdf:lang(zh-CN) .mono { font-family: PT Mono, iawriter-mono, Nitti, Menlo, Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK SC'; }
|
||
.pdf:lang(zh-TW) .mono { font-family: PT Mono, iawriter-mono, Nitti, Menlo, Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK TC'; }
|
||
.pdf:lang(ko-KR) .mono { font-family: PT Mono, iawriter-mono, Nitti, Menlo, Courier, monospace, 'Twemoji', 'Noto Color Emoji', 'Noto Sans Mono CJK KR'; }
|
||
.highlight-default {
|
||
color: rgba(55, 53, 47, 1);
|
||
}
|
||
.highlight-gray {
|
||
color: rgba(120, 119, 116, 1);
|
||
fill: rgba(120, 119, 116, 1);
|
||
}
|
||
.highlight-brown {
|
||
color: rgba(159, 107, 83, 1);
|
||
fill: rgba(159, 107, 83, 1);
|
||
}
|
||
.highlight-orange {
|
||
color: rgba(217, 115, 13, 1);
|
||
fill: rgba(217, 115, 13, 1);
|
||
}
|
||
.highlight-yellow {
|
||
color: rgba(203, 145, 47, 1);
|
||
fill: rgba(203, 145, 47, 1);
|
||
}
|
||
.highlight-teal {
|
||
color: rgba(68, 131, 97, 1);
|
||
fill: rgba(68, 131, 97, 1);
|
||
}
|
||
.highlight-blue {
|
||
color: rgba(51, 126, 169, 1);
|
||
fill: rgba(51, 126, 169, 1);
|
||
}
|
||
.highlight-purple {
|
||
color: rgba(144, 101, 176, 1);
|
||
fill: rgba(144, 101, 176, 1);
|
||
}
|
||
.highlight-pink {
|
||
color: rgba(193, 76, 138, 1);
|
||
fill: rgba(193, 76, 138, 1);
|
||
}
|
||
.highlight-red {
|
||
color: rgba(212, 76, 71, 1);
|
||
fill: rgba(212, 76, 71, 1);
|
||
}
|
||
.highlight-gray_background {
|
||
background: rgba(241, 241, 239, 1);
|
||
}
|
||
.highlight-brown_background {
|
||
background: rgba(244, 238, 238, 1);
|
||
}
|
||
.highlight-orange_background {
|
||
background: rgba(251, 236, 221, 1);
|
||
}
|
||
.highlight-yellow_background {
|
||
background: rgba(251, 243, 219, 1);
|
||
}
|
||
.highlight-teal_background {
|
||
background: rgba(237, 243, 236, 1);
|
||
}
|
||
.highlight-blue_background {
|
||
background: rgba(231, 243, 248, 1);
|
||
}
|
||
.highlight-purple_background {
|
||
background: rgba(244, 240, 247, 0.8);
|
||
}
|
||
.highlight-pink_background {
|
||
background: rgba(249, 238, 243, 0.8);
|
||
}
|
||
.highlight-red_background {
|
||
background: rgba(253, 235, 236, 1);
|
||
}
|
||
.block-color-default {
|
||
color: inherit;
|
||
fill: inherit;
|
||
}
|
||
.block-color-gray {
|
||
color: rgba(120, 119, 116, 1);
|
||
fill: rgba(120, 119, 116, 1);
|
||
}
|
||
.block-color-brown {
|
||
color: rgba(159, 107, 83, 1);
|
||
fill: rgba(159, 107, 83, 1);
|
||
}
|
||
.block-color-orange {
|
||
color: rgba(217, 115, 13, 1);
|
||
fill: rgba(217, 115, 13, 1);
|
||
}
|
||
.block-color-yellow {
|
||
color: rgba(203, 145, 47, 1);
|
||
fill: rgba(203, 145, 47, 1);
|
||
}
|
||
.block-color-teal {
|
||
color: rgba(68, 131, 97, 1);
|
||
fill: rgba(68, 131, 97, 1);
|
||
}
|
||
.block-color-blue {
|
||
color: rgba(51, 126, 169, 1);
|
||
fill: rgba(51, 126, 169, 1);
|
||
}
|
||
.block-color-purple {
|
||
color: rgba(144, 101, 176, 1);
|
||
fill: rgba(144, 101, 176, 1);
|
||
}
|
||
.block-color-pink {
|
||
color: rgba(193, 76, 138, 1);
|
||
fill: rgba(193, 76, 138, 1);
|
||
}
|
||
.block-color-red {
|
||
color: rgba(212, 76, 71, 1);
|
||
fill: rgba(212, 76, 71, 1);
|
||
}
|
||
.block-color-gray_background {
|
||
background: rgba(241, 241, 239, 1);
|
||
}
|
||
.block-color-brown_background {
|
||
background: rgba(244, 238, 238, 1);
|
||
}
|
||
.block-color-orange_background {
|
||
background: rgba(251, 236, 221, 1);
|
||
}
|
||
.block-color-yellow_background {
|
||
background: rgba(251, 243, 219, 1);
|
||
}
|
||
.block-color-teal_background {
|
||
background: rgba(237, 243, 236, 1);
|
||
}
|
||
.block-color-blue_background {
|
||
background: rgba(231, 243, 248, 1);
|
||
}
|
||
.block-color-purple_background {
|
||
background: rgba(244, 240, 247, 0.8);
|
||
}
|
||
.block-color-pink_background {
|
||
background: rgba(249, 238, 243, 0.8);
|
||
}
|
||
.block-color-red_background {
|
||
background: rgba(253, 235, 236, 1);
|
||
}
|
||
.select-value-color-pink { background-color: rgba(245, 224, 233, 1); }
|
||
.select-value-color-purple { background-color: rgba(232, 222, 238, 1); }
|
||
.select-value-color-green { background-color: rgba(219, 237, 219, 1); }
|
||
.select-value-color-gray { background-color: rgba(227, 226, 224, 1); }
|
||
.select-value-color-opaquegray { background-color: rgba(255, 255, 255, 0.0375); }
|
||
.select-value-color-orange { background-color: rgba(250, 222, 201, 1); }
|
||
.select-value-color-brown { background-color: rgba(238, 224, 218, 1); }
|
||
.select-value-color-red { background-color: rgba(255, 226, 221, 1); }
|
||
.select-value-color-yellow { background-color: rgba(253, 236, 200, 1); }
|
||
.select-value-color-blue { background-color: rgba(211, 229, 239, 1); }
|
||
|
||
.checkbox {
|
||
display: inline-flex;
|
||
vertical-align: text-bottom;
|
||
width: 16;
|
||
height: 16;
|
||
background-size: 16px;
|
||
margin-left: 2px;
|
||
margin-right: 5px;
|
||
}
|
||
|
||
.checkbox-on {
|
||
background-image: url("data:image/svg+xml;charset=UTF-8,%3Csvg%20width%3D%2216%22%20height%3D%2216%22%20viewBox%3D%220%200%2016%2016%22%20fill%3D%22none%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3E%0A%3Crect%20width%3D%2216%22%20height%3D%2216%22%20fill%3D%22%2358A9D7%22%2F%3E%0A%3Cpath%20d%3D%22M6.71429%2012.2852L14%204.9995L12.7143%203.71436L6.71429%209.71378L3.28571%206.2831L2%207.57092L6.71429%2012.2852Z%22%20fill%3D%22white%22%2F%3E%0A%3C%2Fsvg%3E");
|
||
}
|
||
|
||
.checkbox-off {
|
||
background-image: url("data:image/svg+xml;charset=UTF-8,%3Csvg%20width%3D%2216%22%20height%3D%2216%22%20viewBox%3D%220%200%2016%2016%22%20fill%3D%22none%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3E%0A%3Crect%20x%3D%220.75%22%20y%3D%220.75%22%20width%3D%2214.5%22%20height%3D%2214.5%22%20fill%3D%22white%22%20stroke%3D%22%2336352F%22%20stroke-width%3D%221.5%22%2F%3E%0A%3C%2Fsvg%3E");
|
||
}
|
||
|
||
</style></head><body><article id="295f378f-c262-45cc-a6de-6acf732f706e" class="page sans"><header><h1 class="page-title">Unit 21: Coulomb’s Law</h1></header><div class="page-body"><h1 id="134d1a28-4600-435c-9206-e23772fa314d" class="">21.1 - Coulomb’s Law</h1><p id="bed27861-f580-4d17-9ad7-ffc134ac518b" class="">The strength of a particle’s electrical interaction with objects around it depends on its electric charge (usually represented as <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>q</mi></mrow><annotation encoding="application/x-tex">q</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span></span></span></span></span><span></span></span>), which can be either positive or negative. Particles with the same sign of charge repel each other, and particles with opposite signs of charge attract each other.</p><p id="e85a469e-e03a-4ad8-b02c-dc09516b1315" class="">An object with equal amounts of the two kinds of charge is electrically <em>neutral</em>, whereas one with an imbalance is electrically charged and has an excess charge.</p><p id="b12d4a72-b93a-4b27-bb16-3a99f87ed4cd" class=""><strong>Conductors </strong>are materials in which a significant number of electrons are free to move. The charged particles in <strong>nonconductors </strong>(insulators) are not free to move.</p><p id="dadc267d-fad5-47fb-b10b-04f5b45ebd08" class=""><strong>Electric current</strong> (<style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi></mrow><annotation encoding="application/x-tex">i</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.65952em;vertical-align:0em;"></span><span class="mord mathnormal">i</span></span></span></span></span><span></span></span>) is the rate <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>q</mi><mi mathvariant="normal">/</mi><mi>d</mi><mi>t</mi></mrow><annotation encoding="application/x-tex">dq/dt</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">d</span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="mord">/</span><span class="mord mathnormal">d</span><span class="mord mathnormal">t</span></span></span></span></span><span></span></span> at which charge passes a point:</p><figure id="0038c33e-0bdf-4bbd-95df-142de0715908" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>i</mi><mo>=</mo><mfrac><mrow><mi>d</mi><mi>q</mi></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac></mrow><annotation encoding="application/x-tex">i = \frac{dq}{dt}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.65952em;vertical-align:0em;"></span><span class="mord mathnormal">i</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:2.0574399999999997em;vertical-align:-0.686em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3714399999999998em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">d</span><span class="mord mathnormal">t</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">d</span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span></span></span></span></div></figure><p id="0decd275-e9be-45c7-97c0-03eafdda8a66" class=""><strong>Coulomb’s law</strong> describes the electrostatic force (or electric force) between two charged particles. If the particles have charges <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msub><mi>q</mi><mn>1</mn></msub></mrow><annotation encoding="application/x-tex">q_1</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:-0.03588em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">1</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span><span></span></span> and <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msub><mi>q</mi><mn>2</mn></msub></mrow><annotation encoding="application/x-tex">q_2</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:-0.03588em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span><span></span></span>, are separated by distance <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi></mrow><annotation encoding="application/x-tex">r</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span></span></span></span></span><span></span></span>, and are at rest (or moving only slowly) relative to each other, then the magnitude of the force acting on each due to the other is given by:</p><figure id="da7a77c9-0c92-48f9-83a9-f60760f83eb3" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>F</mi><mo>=</mo><mfrac><mn>1</mn><mrow><mn>4</mn><mi>π</mi><msub><mi>ϵ</mi><mn>0</mn></msub></mrow></mfrac><mfrac><mrow><mi mathvariant="normal">∣</mi><msub><mi>q</mi><mn>1</mn></msub><mi mathvariant="normal">∣</mi><mi mathvariant="normal">∣</mi><msub><mi>q</mi><mn>2</mn></msub><mi mathvariant="normal">∣</mi></mrow><msup><mi>r</mi><mn>2</mn></msup></mfrac></mrow><annotation encoding="application/x-tex">F = \frac{1}{4\pi\epsilon_0} \frac{|q_1||q_2|}{r^2}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.13889em;">F</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:2.263em;vertical-align:-0.8360000000000001em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.32144em;"><span style="top:-2.3139999999999996em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">4</span><span class="mord mathnormal" style="margin-right:0.03588em;">π</span><span class="mord"><span class="mord mathnormal">ϵ</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">1</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.8360000000000001em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.427em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord"><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.740108em;"><span style="top:-2.9890000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">∣</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:-0.03588em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">1</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord">∣∣</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:-0.03588em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord">∣</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span></span></span></span></div></figure><p id="393b7f38-7ef3-49a2-b1ce-0834f6c678cf" class="">where <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msub><mi>ϵ</mi><mn>0</mn></msub><mo>=</mo><mn>8.85</mn><mo>×</mo><mn>1</mn><msup><mn>0</mn><mrow><mo>−</mo><mn>12</mn></mrow></msup><mtext> </mtext><msup><mi>C</mi><mn>2</mn></msup><mi mathvariant="normal">/</mi><mi>N</mi><mo>⋅</mo><msup><mi>m</mi><mn>2</mn></msup></mrow><annotation encoding="application/x-tex">\epsilon_0 = 8.85 \times 10^{-12} \space C^2/N \cdot m^2</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.58056em;vertical-align:-0.15em;"></span><span class="mord"><span class="mord mathnormal">ϵ</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.72777em;vertical-align:-0.08333em;"></span><span class="mord">8.85</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.064108em;vertical-align:-0.25em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">−</span><span class="mord mtight">12</span></span></span></span></span></span></span></span></span><span class="mspace"> </span><span class="mord"><span class="mord mathnormal" style="margin-right:0.07153em;">C</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mord">/</span><span class="mord mathnormal" style="margin-right:0.10903em;">N</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">⋅</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.8141079999999999em;vertical-align:0em;"></span><span class="mord"><span class="mord mathnormal">m</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span></span></span></span></span><span></span></span> is the permittivity constant. The ratio <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>1</mn><mi mathvariant="normal">/</mi><mn>4</mn><mi>π</mi><msub><mi>ϵ</mi><mn>0</mn></msub></mrow><annotation encoding="application/x-tex">1/4\pi\epsilon_0</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">1/4</span><span class="mord mathnormal" style="margin-right:0.03588em;">π</span><span class="mord"><span class="mord mathnormal">ϵ</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span><span></span></span> is often replaced with the electrostatic constant (or Colulomb’s constant) <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi><mo>=</mo><mn>8.99</mn><mo>×</mo><mn>1</mn><msup><mn>0</mn><mn>9</mn></msup><mi>N</mi><mo>⋅</mo><msup><mi>m</mi><mn>2</mn></msup><mi mathvariant="normal">/</mi><msup><mi>C</mi><mn>2</mn></msup></mrow><annotation encoding="application/x-tex">k = 8.99 \times 10^9 N \cdot m^2/C^2</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.69444em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.72777em;vertical-align:-0.08333em;"></span><span class="mord">8.99</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.8141079999999999em;vertical-align:0em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">9</span></span></span></span></span></span></span></span><span class="mord mathnormal" style="margin-right:0.10903em;">N</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">⋅</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.064108em;vertical-align:-0.25em;"></span><span class="mord"><span class="mord mathnormal">m</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mord">/</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.07153em;">C</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span></span></span></span></span><span></span></span>.</p><h2 id="540f07ff-2c32-4d30-95c3-8d24cc8f9776" class="">Units</h2><p id="44a5ae4a-4687-48e7-9d83-92f94672de23" class="">The <strong>coulomb</strong>, the SI unit of charge, is derived from the SI unit <em>ampere </em>for electric current.</p><figure id="9fd2a904-a394-48ce-94cc-998fb8ac8692" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>1</mn><mtext> C</mtext><mo>=</mo><mo stretchy="false">(</mo><mn>1</mn><mtext> A</mtext><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mn>1</mn><mtext> s</mtext><mo stretchy="false">)</mo></mrow><annotation encoding="application/x-tex">1 \space \textrm{C} = (1\space\textrm{A})(1\space\textrm{s})</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord">1</span><span class="mspace"> </span><span class="mord text"><span class="mord textrm">C</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord">1</span><span class="mspace"> </span><span class="mord text"><span class="mord textrm">A</span></span><span class="mclose">)</span><span class="mopen">(</span><span class="mord">1</span><span class="mspace"> </span><span class="mord text"><span class="mord textrm">s</span></span><span class="mclose">)</span></span></span></span></span></div></figure><p id="14e67b98-527a-40be-949b-e9b373c856f3" class="">The electrostatic force vector acting on a charged particle due to a second charged particle is either directly toward the second particle (opposite signs of charge) or directly away from it (same sign of charge).</p><p id="b4ba913a-e9d3-48d1-a965-85fbe1527e06" class="">If multiple electrostatic forces act on a particle, the net force is the vector sum (not scalar sum) of the individual forces.</p><h2 id="1abbed4d-f569-4d76-b15e-ae79dda6c142" class="">Shell Theorems</h2><ul id="6ab8f711-3a83-46dc-bd6f-41d9092cf9b6" class="bulleted-list"><li style="list-style-type:disc"><strong>Shell Theorem 1:</strong> A charged particle outside a shell with charge uniformly distributed on its surface is attracted or repelled as if the shell's charge were concentrated as a particle at its center.</li></ul><ul id="ca7a3b33-e4d7-4a8c-bbb4-7a49ba03110a" class="bulleted-list"><li style="list-style-type:disc"><strong>Shell Theorem 2:</strong> A charged particle inside a shell with charge uniformly distributed on its surface has no net force acting on it due to the shell.</li></ul><ul id="c8d1bf69-a823-4184-bae1-775713ac0f53" class="bulleted-list"><li style="list-style-type:disc">Charge on a conducting spherical shell spreads uniformly over the (external) surface.</li></ul><h1 id="384a6a19-f361-4823-acdf-fbbef4244588" class="">21.2 - Charge is Quantized</h1><p id="703c4f70-2095-4e63-b7cd-5c5c0dd2395d" class="">Electric charge is <strong>quantized</strong>, or restricted to certain values. Because each particle (proton and electron) has the same charge:</p><figure id="ac875899-b1e4-48a7-84e1-e38f45513cf9" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>e</mi><mo>=</mo><mn>1.602</mn><mo>×</mo><mn>1</mn><msup><mn>0</mn><mrow><mo>−</mo><mn>19</mn></mrow></msup><mtext> C</mtext></mrow><annotation encoding="application/x-tex">e = 1.602 \times 10^{-19} \space \textrm{C}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.72777em;vertical-align:-0.08333em;"></span><span class="mord">1.602</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.864108em;vertical-align:0em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.864108em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">−</span><span class="mord mtight">19</span></span></span></span></span></span></span></span></span><span class="mspace"> </span><span class="mord text"><span class="mord textrm">C</span></span></span></span></span></span></div></figure><p id="6b80b02e-4b0a-4cd8-bced-cf5df88b79e9" class="">then every possible electric charge is some multiple of this base charge, the <strong>elementary charge</strong>. Therefore, any positive or negative charge <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>q</mi></mrow><annotation encoding="application/x-tex">q</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span></span></span></span></span><span></span></span> that can be detected can be written as:</p><figure id="2e1c98ef-3c8c-4e16-b484-b63eaf0f4b72" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>q</mi><mo>=</mo><mi>n</mi><mi>e</mi><mo separator="true">,</mo><mspace width="2em"/><mi>n</mi><mo>=</mo><mo>±</mo><mn>1</mn><mo separator="true">,</mo><mo>±</mo><mn>2</mn><mo separator="true">,</mo><mo>±</mo><mn>3</mn><mo separator="true">,</mo><mi mathvariant="normal">.</mi><mi mathvariant="normal">.</mi><mi mathvariant="normal">.</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">q = ne, \hspace{2em} n = \pm 1, \pm 2, \pm 3, ...,</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal">n</span><span class="mord mathnormal">e</span><span class="mpunct">,</span><span class="mspace" style="margin-right:2em;"></span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.8388800000000001em;vertical-align:-0.19444em;"></span><span class="mord">±</span><span class="mord">1</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord">±</span><span class="mord">2</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord">±</span><span class="mord">3</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord">...</span><span class="mpunct">,</span></span></span></span></span></div></figure><h1 id="cf83c647-a9f5-4b6f-b1f2-79273f225eca" class="">21.3 - Charge is Conserved</h1><figure class="block-color-gray_background callout" style="white-space:pre-wrap;display:flex" id="6dafd782-38ba-44cd-925c-1e5c3ecebeb8"><div style="font-size:1.5em"><span class="icon">💡</span></div><div style="width:100%"><strong>Key Idea
|
||
</strong>The net electric charge of any isolated system is <em>always </em>conserved.</div></figure><h2 id="bf984fce-a0bb-4b89-90d8-39801dd779cb" class="">Annihilation Process</h2><p id="6575b69b-4bbb-452c-903f-d68fa8ba456b" class="">An annihilation process occurs when an electron <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mi>e</mi><mo>−</mo></msup></mrow><annotation encoding="application/x-tex">e^-</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.771331em;vertical-align:0em;"></span><span class="mord"><span class="mord mathnormal">e</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">−</span></span></span></span></span></span></span></span></span></span></span></span><span></span></span> (charge <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo>−</mo><mi>e</mi></mrow><annotation encoding="application/x-tex">-e</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.66666em;vertical-align:-0.08333em;"></span><span class="mord">−</span><span class="mord mathnormal">e</span></span></span></span></span><span></span></span>) and its antiparticle, the positron <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mi>e</mi><mo>+</mo></msup></mrow><annotation encoding="application/x-tex">e^+</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.771331em;vertical-align:0em;"></span><span class="mord"><span class="mord mathnormal">e</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">+</span></span></span></span></span></span></span></span></span></span></span></span><span></span></span> (charge <style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><span data-token-index="0" contenteditable="false" class="notion-text-equation-token" style="user-select:all;-webkit-user-select:all;-moz-user-select:all"><span></span><span><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>e</mi></mrow><annotation encoding="application/x-tex">e</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathnormal">e</span></span></span></span></span><span></span></span>), undergo , transforming into two gamma rays (high-energy light):</p><p id="ed3dac3f-3919-4a82-a25d-46452b22f35e" class="">If two charged particles undergo an annihilation process, they have opposite signs of charge.</p><p id="7d99b36f-8bb1-4700-9007-d59f58770a2a" class="">If two charged particles appear as a result of a pair production process, they have opposite signs of charge.</p><figure id="527782f6-0a45-4fd1-814c-60ead9cbad2b" class="equation"><style>@import url('https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.13.2/katex.min.css')</style><div class="equation-container"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><msup><mi>e</mi><mo>−</mo></msup><mo>+</mo><msup><mi>e</mi><mo>+</mo></msup><mo>→</mo><mi>γ</mi><mo>+</mo><mi>γ</mi></mrow><annotation encoding="application/x-tex">e^- + e^+ \rightarrow \gamma + \gamma</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.904661em;vertical-align:-0.08333em;"></span><span class="mord"><span class="mord mathnormal">e</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.821331em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">−</span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.821331em;vertical-align:0em;"></span><span class="mord"><span class="mord mathnormal">e</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.821331em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">+</span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">→</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.7777700000000001em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.05556em;">γ</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.05556em;">γ</span></span></span></span></span></div></figure><p id="8651116f-1ffa-4a51-bafe-fff1d226e612" class="">
|
||
</p></div></article></body></html> |