Electrostatics - part 4 of 4 — Transcript

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1. 0:00out and the i would say it is now
2. 0:02negative
3. 0:04and just to demonstrate if i bring a
4. 0:05negative near it watch the leaf move
5. 0:07further out
6. 0:09but if i bring a positive near it
7. 0:13watch the leaf collapse
8. 0:18[Music]
9. 0:20and so anything that makes the lease
10. 0:21collapse must be positive anything that
11. 0:23makes the leaf move out must be
12. 0:24negative so that's the answer to 24
13. 0:26that's your description and then 25 says
14. 0:28actually give this a try so the first
15. 0:30part of 25 says take the glass rod
16. 0:32got it and rub it with fur okay so
17. 0:35here's a piece of fur
18. 0:37and this in case you're wondering is
19. 0:39kind of the classical experiment this is
20. 0:41what
21. 0:41benjamin franklin did
22. 0:44and we get a lot of our names from
23. 0:46electricity from this experiment here
24. 0:49and so what happens with glass glass and
25. 0:52fur
26. 0:54we know that they're going to rub and
27. 0:56bump off electrons and one of them
28. 0:58either the fur or the glass is going to
29. 1:00suck in those electrons but which one
30. 1:03so let's see what happens to glass does
31. 1:06it make the leaf go up or down looks
32. 1:08like it's going
33. 1:09which way down
34. 1:12so i'd say this must be positive so the
35. 1:15fur has a greater affinity for electrons
36. 1:17than
37. 1:18the glass so the glass when rubbed with
38. 1:21fur
39. 1:22is positive how about the glass when it
40. 1:24is rubbed with wool
41. 1:27okay
42. 1:33let's see does the leaf go up or down
43. 1:35looks like it's down
44. 1:36looks like it's down a lot more so i
45. 1:40would say
46. 1:41it's still positive and it's actually
47. 1:43not too much of a surprise
48. 1:45fur and wool aren't that much different
49. 1:47uh they
50. 1:48are very electronegative compared to
51. 1:50glass
52. 1:52this is a little more electronegative
53. 1:54the wool than the fur
54. 1:56so the glass becomes positive either way
55. 1:59and i would even say a little more
56. 2:01positive now
57. 2:03and so let's try rubber
58. 2:06the first one says rubber with fur okay
59. 2:09so let's grab the fur
60. 2:12and rub it
61. 2:16and just on the fact that he switched
62. 2:17materials probably makes you guess
63. 2:19that i bet the leaf moves out there we
64. 2:22go
65. 2:23not by much but it does move out
66. 2:28so i would say this is negative
67. 2:32[Music]
68. 2:35and then if i take the rubber and the
69. 2:38wool
70. 2:47we might get
71. 2:51a positive i was hoping to get a
72. 2:55negative
73. 2:56but remember i said this was really
74. 2:57electronegative and so it looks like it
75. 2:59overpowered the
76. 3:02rubber and not much can overpower the
77. 3:07rubber fur can't do it
78. 3:11so the fur is positive yeah but the wool
79. 3:14can
80. 3:17yeah see yes
81. 3:20yeah there goes down uh how about paper
82. 3:24well maybe i better stop there but again
83. 3:26there's a battle going on between the
84. 3:27two materials
85. 3:28and so whether they become positive or
86. 3:30whether they become negative
87. 3:32and so franklin noticed that
88. 3:38glass seemed to be a material that
89. 3:40seemed to always lose its electrons and
90. 3:42so he said let's make these by
91. 3:45definition
92. 3:46positive whatever's going on he called
93. 3:48them positive
94. 3:49and rubber
95. 3:53as you can see not all the time but most
96. 3:54of the time sucked in the
97. 3:56electrons there's a few things that
98. 3:58sucked it a little bit more so he
99. 3:59decided to
100. 4:00use this as its definition of negatives
101. 4:03and so that was kind of the beginning of
102. 4:05the
103. 4:05positive and negative story all right
104. 4:08well
105. 4:09i guess i'm getting close to two hours
106. 4:11here so i apologize for being
107. 4:12long-winded
108. 4:13but i think we covered some really good
109. 4:14stuff as well as got you hopefully ready
110. 4:18for understanding how we'll kind of do
111. 4:19the labs here in the in the in the
112. 4:21future
113. 4:21so here's what i want you to do uh
114. 4:23sometime between
115. 4:25now and sunday night i will go to canvas
116. 4:29and i will make it available that you
117. 4:31can take your lab
118. 4:33and put it in a pdf form
119. 4:36actually i'll i'll set it up so you can
120. 4:38turn in any form but i prefer a pdf form
121. 4:40so if you have the
122. 4:41ability and the knowledge of how to do a
123. 4:42pdf form please submit a pdf form canvas
124. 4:45works best with pdf
125. 4:47it uh the pictures work okay but they're
126. 4:50not that great and then even some of the
127. 4:52other
128. 4:52formats are are okay but but pdf is
129. 4:56is is best so if you know how to convert
130. 4:58things to a pdf
131. 5:00please convert this the answer to these
132. 5:0225 to a pdf but also before you turn it
133. 5:04in
134. 5:05answer those six discussion questions
135. 5:08and they're pretty much what stuff we've
136. 5:10already answered so if you uh need to
137. 5:12re-watch this a second time
138. 5:14to answer those go ahead and do that but
139. 5:16you uh
140. 5:17when you look at this you'll you'll see
141. 5:19that i did explain all of these and so
142. 5:21answer these
143. 5:22six and so that's what you'll be uh
144. 5:24turning in and so
145. 5:25like i said if you're uh if you get this
146. 5:28video
147. 5:28tonight monday night you start working
148. 5:30on it you may not be able to turn it
149. 5:32into canvas i gotta
150. 5:33go back into canvas and figure out how
151. 5:36you can submit it and i got a lot to
152. 5:37learn myself
153. 5:38but you will definitely be turning it in
154. 5:41there with with the canvas all right
155. 5:43well with that said i'll close here for
156. 5:45today
157. 5:45and shoot me an email if you've got any
158. 5:48questions
159. 5:49thanks