Фізика 9 НУШ. Лабораторна робота №3. Дослідження електричного опору кола з напівпровідниковим діодом — Transcript

Full transcript

1. 0:00Greetings. Today, we will conduct a
2. 0:02laboratory experiment. Write down the
3. 0:05date. Laboratory experiment number
4. 0:07three. Topic: Investigation of the
5. 0:10electrical resistance of a circuit with
6. 0:13a semiconductor diode. Next, write down
7. 0:16the objective and equipment. Objective:
8. 0:20To verify experimentally how a
9. 0:22semiconductor diode operates in a DC
10. 0:26circuit. To determine how the current
11. 0:30through the diode changes with varying
12. 0:32voltage in forward bias. To verify that
13. 0:36the diode allows almost no current to
14. 0:38pass when the polarity is reversed.
15. 0:41This is called reverse bias. Next,
16. 0:44write down the equipment. You can
17. 0:47immediately see the equipment I have
18. 0:49used. So, we have a semiconductor diode
19. 0:54, a DC power source. A voltmeter, an
20. 0:58ammeter, a slide rheostat, a switch,
21. 1:02and connecting wires. We will conduct
22. 1:07this lab remotely, meaning I will
23. 1:10perform it myself, while you follow
24. 1:14along and take readings from the
25. 1:17instruments with me. That is, we must
26. 1:21record the current for different
27. 1:23voltages. You will see these values on
28. 1:26the connected instruments. Of course,
29. 1:30those who have the opportunity can
30. 1:32perform this lab in person at school
31. 1:35and see everything with their own eyes.
32. 1:38So, let's proceed to the experiment.
33. 1:41And before starting, I remind you once
34. 1:44again that when performing any
35. 1:46laboratory or experimental work, one
36. 1:49must strictly follow safety rules. And
37. 1:53carefully follow the instructions. The
38. 1:56measurement and calculation data you
39. 1:59see on the screen today should be
40. 2:01entered immediately into the table that
41. 2:04will appear on the screen shortly. So,
42. 2:08let’s first examine the experiment
43. 2:10with the semiconductor diode in forward
44. 2:13bias. Task one. Draw the electrical
45. 2:17circuit diagram according to the figure
46. 2:19. You can see this figure on the right.
47. 2:23While solving problems, we saw several
48. 2:25circuits where a diode was connected.
49. 2:28Therefore, those who carefully watched
50. 2:31the previous lesson know exactly how to
51. 2:33connect it. Forward bias, as you
52. 2:37remember, is a connection where the
53. 2:40arrow, which can be distinguished in
54. 2:43the diode symbol, points from the plus
55. 2:46to the minus. Next, task two. Assemble
56. 2:50the electrical circuit according to the
57. 2:52drawn diagram using the available
58. 2:54equipment. As you have all noticed, I
59. 2:56have assembled this circuit. Ensure
60. 2:58that the diode is connected in the
61. 3:00forward direction. Anode to positive,
62. 3:03cathode to negative. I have verified
63. 3:06and see that I connected everything
64. 3:08correctly. Each diode may differ in
65. 3:12both appearance and the symbols marked
66. 3:15on it. Therefore, it is not always
67. 3:19quick and simple to do. Next, task
68. 3:22three. Close the circuit. Using the
69. 3:26rheostat, set the lowest possible
70. 3:28voltage across the diode. Take the
71. 3:31first readings of the voltage across
72. 3:33the diode and the forward current
73. 3:35through it. Of course, you first need
74. 3:39to draw the table. I suggest adding two
75. 3:42more columns to it because I made more
76. 3:45measurements. Eleven, so that the graph
77. 3:49is much more accurate. As everyone has
78. 3:52already seen, I set the minimum voltage
79. 3:56to 0.5 V. My ammeter showed a current
80. 3:59of 0.4. And we enter these values into
81. 4:04the table. Next is task four. By moving
82. 4:08the rheostat slider, gradually increase
83. 4:10the voltage across the diode. After
84. 4:13each change, measure the voltage U and
85. 4:16the forward current. After completing
86. 4:18all the tests, open the circuit. But
87. 4:21pay attention, there is a warning. The
88. 4:24forward current of the diode must not
89. 4:27exceed its maximum value. In most cases
90. 4:30, this is 0.3. And a higher current can
91. 4:33damage the diode. My diode is
92. 4:36specifically for rectifying high
93. 4:39currents. It can withstand a current of
94. 4:435 A. Therefore, in this case, I must
95. 4:46not exceed 5 A. And the next point.
96. 4:50During the experiment, you must perform
97. 4:53at least seven measurements. Seven is
98. 4:56the optimal number for building a
99. 4:58reliable graph. Of course, the more
100. 5:00measurements, the more accurately the
101. 5:02relationship is reflected and the
102. 5:04better the consistency of the
103. 5:06experimental data will be. As I said at
104. 5:09the beginning, I performed 11
105. 5:11measurements, so the graph will be
106. 5:13quite accurate, meaning we will have
107. 5:16the true current-voltage characteristic
108. 5:19of this diode. And so, we follow
109. 5:22carefully and record all data in the
110. 5:25table. The second measurement is 1 Volt
111. 5:29. The current is 0.27. And, of course,
112. 5:34the rheostat does not allow for very
113. 5:37precise voltage settings, so everything
114. 5:40will be approximate. Therefore, we will
115. 5:43have a certain margin of error. Next,
116. 5:46we have 1.2 V, which I set, and the
117. 5:48current is approximately 0.41. Amperes.
118. 5:54At a voltage of 1.3 V, the current is
119. 5:590.44. And at a voltage of 1.4 V, the
120. 6:05current reached half an ampere, 0.5.
121. 6:12Next, at a voltage of 1.5 V, we have a
122. 6:14current of 0.56. Amperes at a voltage
123. 6:20of 1.6 V, we have 0.61. And at a
124. 6:26voltage of 1.7 V, approximately 0.65.
125. 6:32And at a voltage of 1.8 V, 1. A. At 1.9
126. 6:42Volts, we have 0.77. And the last value
127. 6:49. At 2 Volts, the current passing
128. 6:52through with forward connection is 0.82
129. 6:55. And if you have recorded that, let's
130. 7:00move on to task five. Using the table
131. 7:04data, plot the graph of the current
132. 7:06passing through the diode versus the
133. 7:09voltage across it, that is, I versus U
134. 7:11for forward bias, as in the sample.
135. 7:15This will be the so-called
136. 7:17current-voltage characteristic of this
137. 7:19diode. Of course, it is best to do this
138. 7:23on graph paper, but as a last resort,
139. 7:26you can simply use a squared notebook.
140. 7:30If you have finished that, there is a
141. 7:32second part to this experiment. We will
142. 7:35now test the reverse connection of the
143. 7:38semiconductor diode. Task one. Change
144. 7:42the polarity of the power source
145. 7:44connection or turn the diode around so
146. 7:46that the diode is in the reverse
147. 7:48direction. Anode to minus, cathode to
148. 7:51plus. I will turn the diode around.
149. 7:53After all, changing the polarity of the
150. 7:55source would require changing the
151. 7:58polarity on all measuring instruments.
152. 8:00That is not very convenient. There, the
153. 8:03diode polarity is changed. Next, task
154. 8:06two. Close the circuit, smoothly change
155. 8:09the voltage across the diode using the
156. 8:11rheostat, and observe the ammeter. As
157. 8:14you can see, the ammeter shows zero.
158. 8:18But let's switch to microammeter mode
159. 8:20just for interest. Here you can see
160. 8:24that even when changing the voltage, we
161. 8:27have small currents, but we can see by
162. 8:30the values that they are truly very,
163. 8:33very negligible. And based on what you
164. 8:36have seen, you need to make a brief
165. 8:39observation record, indicating whether
166. 8:41the ammeters showed any values after
167. 8:44changing the polarity. And if they did
168. 8:47show something, was it noticeable or
169. 8:49just barely? And finally, you need to
170. 8:53record what conclusion follows from
171. 8:56this: whether current flows, or hardly
172. 8:58flows at all, when the semiconductor
173. 9:01diode is reverse-biased. We saw all of
174. 9:05this from the second experiment. After
175. 9:08recording, let's move on to the
176. 9:09conclusion. Formulate a conclusion
177. 9:12where you state, first, the operation
178. 9:14of which device you investigated in
179. 9:16this laboratory work. Second. Does this
180. 9:20device conduct electric current equally
181. 9:22in the forward and reverse directions?
182. 9:25Third. What is the nature of the
183. 9:28dependence of the current through the
184. 9:30diode on the voltage across it when
185. 9:32forward-biased? Linear or nonlinear?
186. 9:36How is this visible from the I-V graph,
187. 9:38that is, the current-voltage
188. 9:40characteristic? Write it down. Next. Of
189. 9:44course, as always, a check question.
190. 9:47Task one. The figure shows three
191. 9:50electrical circuits A, B, and C with a
192. 9:53current source, a light bulb, and a
193. 9:56semiconductor diode connected in
194. 9:58different positions. Determine in which
195. 10:02case the bulb will light up and in
196. 10:05which it won't, and explain your answer
197. 10:07by showing when the diode is
198. 10:09forward-biased and when it is
199. 10:11reverse-biased. And how this affects
200. 10:15the direction and presence of current
201. 10:16in the circuit. We can see in figure C
202. 10:19that we even have two diodes. We had a
203. 10:22similar task while solving problems.
204. 10:24Anyone who doesn't know how to answer
205. 10:26can watch the previous lesson. Next,
206. 10:29task two. A current of 0.2 A flows
207. 10:32through a semiconductor diode in the
208. 10:35forward direction at a voltage of 4 V.
209. 10:37Determine the electrical resistance of
210. 10:40the diode in this mode. A hint is to
211. 10:44use Ohm's law for a circuit section,
212. 10:46but solve it as a problem, that is,
213. 10:49with a short summary. And the third
214. 10:52task is also a problem. At a voltage of
215. 10:556 V, the current through the diode when
216. 10:58forward-biased is 0.3 A, and when
217. 11:00reverse-biased it is 0.3 [microamps].
218. 11:05And by how many times can the current
219. 11:07be greater in the forward direction
220. 11:09than in the reverse? Draw a conclusion
221. 11:12about the conductivity of the diode in
222. 11:14different directions. If the questions
223. 11:17and problems are completed, let's move
224. 11:19on to the creative task. Conduct a
225. 11:23similar study for another semiconductor
226. 11:25element. Record the current-voltage
227. 11:28characteristic (I vs U) during forward
228. 11:31biasing. Verify the practical absence
229. 11:35of current during reverse biasing and
230. 11:38compare the results obtained with the
231. 11:40characteristics of the semiconductor
232. 11:42element studied in the main part of the
233. 11:45work. Based on the comparison,
234. 11:49formulate a conclusion about the
235. 11:50differences in their electrical
236. 11:52properties. To make the task even more
237. 11:56interesting, this time I will take an
238. 11:59LED, that is, a diode that can light up
239. 12:01when current passes through it. And now
240. 12:05you can track its current and voltage.
241. 12:09But pay attention, I am supplying
242. 12:12voltage in volts, and the current
243. 12:14initially in microamperes. Here we can
244. 12:18see these values. So, as we can see,
245. 12:20the current is very, very small. And
246. 12:23now I have switched the tester, my
247. 12:26ammeter in this case, to milliammeter
248. 12:29mode. That means the values are now
249. 12:32displayed in milliamperes. And that was
250. 12:34the forward bias connection. You
251. 12:37noticed that as the voltage and current
252. 12:40increase, the diode glows brighter and
253. 12:43brighter. And now, reverse bias
254. 12:45connection. In this case, you can see
255. 12:49that there is practically no current.
256. 12:53To make writing your conclusion easier,
257. 12:56you can draw another table, list the
258. 12:58current values for the corresponding
259. 13:01voltages, take several values, for
260. 13:03example, seven, and plot another graph.
261. 13:08That is, create a current-voltage
262. 13:10characteristic for the LED. And this
263. 13:13will help you better formulate the
264. 13:16conclusion for your creative task and
265. 13:18get a fairly high score. That is all
266. 13:22for now. Process your results and later
267. 13:25review section eight again. I am not
268. 13:28assigning any homework exercises this
269. 13:30time. In the next two lessons, we will
270. 13:33be preparing for the summative
271. 13:35assessment. Therefore, I advise you to
272. 13:38watch the upcoming videos as well. See
273. 13:41you later.