I Just Want to Be a Quiet Top Student

　　 "In the past, I had no choice. Now, I just want to be a quiet schoolmaster." Shen Qi said from the bottom of his heart.

　　 "You just pretend to be quiet, Mr. Shen Qi!" The boy wiped away his tears and stopped crying. The boy should be self-improvement. He asked, "By the way, how much did you score in the theory test?"

　　 "280."

　　 "I...I'm seriously unwell...I want to report you, Shen Qi!" The boy slammed a fist on the tree next to him.

　　 "Please don't do this, my friend." Shen Qi stood up, turned around and prepared to leave.

　　 "Wait for the boss!" The boy grabbed Shen Qi's arm, and said eagerly, "Do you have a pen with you? The pen for the exam yesterday."

　　 There is a pen in Shen Qi's pocket. Mu Rong gave it to him when filling out the form just now, but Mu Rong forgot to take it.

　　 "Here, I'll give it to you." Shen Qi took out the ink pen and handed it to the boy.

"Thank you, boss!" The boy took Shen Qi's pen and swept away his decline: "Magic pen in hand, no worries about the exam! Master Shen Qi, I wish you a steady progress on the road of pretending to be promoted to Yan University as soon as possible. A new generation of kings!"

　　...

　　 The next day, the CPhO experiment is in progress.

　　 80 points for experimental questions and 280 points for theoretical questions.

　　Experiment + theory is the total result of this national final.

　　 Shen Qi got a full score of 280 in the theory test the day before yesterday. As long as he doesn't make low-level mistakes in today's experiment session, his total score will enter a higher range.

　　 Why did the player from Suzhou-Hangzhou No. 2 Middle School we met yesterday cry, because his theoretical score was only 172 points. Even if he gets a full score of 80 in the experiment, his total score cannot be higher than Shen Qi's theoretical score.

　　Theoretical examination is of course the highlight of the national finals, but the experimental questions cannot be relaxed.

　　 All contestants are divided into two groups, one in the morning and one in the afternoon. The experimental questions in the morning and afternoon are all electrical experiments. The questions are different but the difficulty is similar.

　　 Shen Qi draws the lottery to do experimental questions in the afternoon.

　　 The experimental instruments and utensils distributed by the invigilators are:

1 DC stabilized power supply, 2 digital multimeters, 2 potentiometers, 1 standard resistance box, 1 DC galvanometer, 1 constant temperature water bath, 1 diode to be tested, 1 programmable calculator, wire Several.

　　The experimental requirements are:

　　 Design an experiment based on a given experimental instrument to accurately measure the forward volt-ampere characteristics of the diode at t=27°C. The current change range is 0.5-1000μA, and it is required to measure no less than 20 sets of data.

　　 And, draw a circuit diagram, explain the experimental principle, write out the experimental steps, design a table to record the experimental data. Also draw the diode forward volt-ampere characteristic curve, get the reverse saturation current I0, ideal factor n.

　　 If you have completed the steps described above and got the correct result, it is not over yet, please continue below:

When the current in the diode is constant, set the diode current to be 5μA, 15μA, 20μA, try to determine the relationship between voltage and temperature, derive the diode voltage Vg(0) at absolute zero, and analyze under different constant current conditions , The characteristics of the diode forward junction voltage and its causes when the absolute zero is obtained.

　　 The above is the question stem requirement given on the experimental answer sheet.

　　 This experimental question is not difficult, but 80 points are not so easy to get all. In addition to the accuracy of the steps and results written on the answer sheet, the actual behavior of the contestants is also counted in the scoring or deduction items.

　　 The invigilator inspects in the laboratory and records the actual behavior of each player. One-on-one tracking is impossible. There are not so many invigilators. Generally, an invigilator stares at several players around, so today’s experiment will be divided into two sessions in the morning and afternoon to divert the players.

　　 Shen Qi has practiced under the guidance of Mu Rong, and has practiced electrical experiments.

　　 The experiment question for the rematch is also electricity, and the final is still.

　　Because the electrical experimental equipment is simple and easy to obtain, the experimental results can be verified on the spot, and it is easy to set up as a competition experiment.

　　 Each contestant has a particle accelerator. The Chinese Physical Society does not have the ability and financial resources. The Chinese Physical Society's headquarters has a particle accelerator, which is still second-hand.

　　 Shen Qi first used the bridge method to draw the measurement circuit diagram, and then set the temperature of the water bath to 27 degrees.

　　 Connect the circuit according to the circuit diagram, adjust the initial value of the potentiometer, make the output voltage of the voltage divider circuit 0, set the value of the resistance box to 10,000 Ω, and adjust the galvanometer to zero.

　　 After completing these basic experimental preparations, Shen Qi turned on the power and slowly adjusted the potentiometer to increase the reading of the ammeter.

　　 Continue to adjust and repeatedly adjust the potentiometer and resistance box to make the bridge in equilibrium at the set voltage value.

　　 Then Shen Qi drew a record form on the answer sheet and recorded the data.

　　Voltage 0.430V, current 0.52μA

　　Voltage 0.441V, current 0.77μA

　　...

　　 20 sets of data were recorded. Shen Qi drew the diode forward volt-ampere characteristic curve based on these data, and calculated the reverse saturation current I0=3.397×10^-14A, and the ideality factor n=1.001.

　　 The first small part of this experiment is completed.

　　 Up to this point, it is the basic electrical experiment operations that high school students need to master, as well as the basic abilities of data recording, processing, and calculation.

　　 So the experimental link can’t get the scores, let alone the candidates, ordinary high school students, physics scores are so-so, the kind of hands-on ability is still good, it is fine to finish the first small part of the national finals experimental questions.

　　 The second part is a little more troublesome.

　　 derive the diode voltage Vg(0) at absolute zero, analyze the characteristics of the diode forward junction voltage at absolute zero and its cause under different constant current conditions, this is actually a theoretical derivation calculation problem.

　　 The CPhO test comes and goes, to put it plainly is to test theoretical knowledge.

　　 After theoretical derivation and calculation, Shen Qi found that Vg(0) is 1.225V, 1.233V, and 1.244V when it is infinitely close to absolute zero. These three voltage values ​​correspond to current values ​​of 5μA, 10μA, and 15μA, respectively.

　　This is the end of the experimental session.

　　 Many players, including Shen Qi, successfully completed the experiment and answered the questions.

　　 The scores of the experimental questions were announced on the same day.

　　 No contestant got a full score of 80 points for the experimental questions, and the highest score was 79.5 points. UU reading www.uukanshu.com

　　 In this part of the actual exercises, each player was deducted a little bit more or less.

　　 There is no way to do this. There is no standard posture for the actual operation. No one can guarantee that every detail of oneself is perfect.

　　 Shen Qi scored 77 points in the experiment and was deducted 3 points. He can accept this result.

　　 The experimental scores came out, which means that the total scores of the current CPhO national finals have been finalized.

　　The Chinese Physics Society announced the total score ranking of each contestant:

　　1, Shen Qi (Nangang No. 2 Middle School), 357 points;

　　2, Tang Mengqi (Changjun Middle School), 352.5 points;

　　3, Su Xiaolie (No. 1 Middle School of China Normal University), 352 points;

　　4, Lu Huaisong (Suhang No. 2 Middle School), 350.5 points;

　　 5. Ma Zixin (Yali Middle School), 349 points;

　　 5. Han Xuance (Shijiacun No. 2 Middle School), 349 points

　　 7, Jin Shengqiang (Special Zone Middle School), 348.5 points;

　　...

　　200, Zeng Luna (Northeast Yucai School), 112 points.

　　 The total score is only announced to the top 200, among which the top 50 won the national first prize, 51-200 won the national second prize, and 201-412 were all third prizes.

　　 The national gold medal score line reached 282 points, which is the score of the 50th player.

　　 The national training team scored 298 points, which is the score of the 40th player.

　　 The dust settled, 50 players won the first national gold medal, among which the top 40 gold medalists were selected for the national training team of the competition.

　　 As in the past, the top 50 players are basically from domestic competitive sports schools and academic competition schools.

　　 Except for Shen Qi, who is ranked number one.