I Just Want to Be a Quiet Top Student

"In the past, I didn't have a choice. Now, I just want to be a quiet top student." Shen Qi said from the bottom of his heart.

"Just pretend to be coquettish quietly, Boss Shen Qi!" The boy wiped away his tears and stopped crying, and he asked, "By the way, what score did you score in this theory test?"

"280."

"I...I'm seriously unwell...I want to report you, Shen Qi!" The boy punched the big tree next to him.

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

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

Shen Qi had a pen in his pocket, which was given to him by Mu Rong when he was filling out the form just now, but Mu Rong forgot to take it away.

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

"Thank you, big brother!" The boy took Shen Qi's pen and swept away his weakness: "With the magic pen in hand, the exam is worry-free! Boss Shen Qi, I wish you steady progress on the road of pretending to be aggressive, and you will be promoted to Yanda University as soon as possible. A new generation of kings!"

...

The next day, the CPhO experiment was in progress.

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

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

Shen Qi got a perfect 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, his total score will enter a higher range.

Why did the contestant from Suzhou-Hangzhou No. 2 Middle School I met yesterday cry? Because his theoretical score was only 172 points. Even if he got a perfect score of 80 in the experiment, his total score could not be higher than Shen Qi's theoretical score.

The theoretical test is of course the highlight of the national finals, but the experimental questions cannot be slackened.

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 got the lottery to do the experimental questions in the afternoon.

The experimental instruments and utensils issued 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, wires Several.

The experimental requirements are:

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

And, draw a circuit diagram, explain the principle of the experiment, write the experimental steps, and design a table to record the experimental data. It is also necessary to draw the forward volt-ampere characteristic curve of the diode to obtain the reverse saturation current I0 and the ideality factor n.

If the above steps are completed and the correct result is obtained, it is not finished yet, please continue below:

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

The above are the requirements for the questions given on the answer sheet of the experiment.

This experimental question is not difficult, but it is not so easy to get 80 points. 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 deducting items.

The invigilator patrols the laboratory and records the practical behavior of each contestant. One-on-one marking is impossible, and there are not so many invigilators. Generally, an invigilator keeps an eye on several contestants around, so today's experiment session is divided into two sessions in the morning and afternoon to divide the contestants.

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

The experimental questions in the semi-finals were also electricity, and the finals were the same.

Because the electrical experiment 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, and the Chinese Physics Society does not have the ability and financial resources to organize it. The headquarters of the Chinese Physics Society only 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 so that the output voltage of the voltage divider circuit is 0, set the value of the resistance box to 10,000Ω, 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 adjust the potentiometer and resistance box repeatedly, so that the bridge is in balance at the set voltage value.

Then Shen Qi drew a recording form on the answer sheet to record the data.

Voltage 0.430V, current 0.52μA

Voltage 0.441V, current 0.77μA

...

After recording 20 sets of data, Shen Qi drew the forward volt-ampere characteristic curve of the diode 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 complete.

Until here, it is the basic electrical experiment operation that high school students need to master, as well as the basic abilities of data recording, processing, and calculation.

Therefore, the experimental part cannot be divided into scores, let alone physical contestants. Ordinary high school students with so-so physics scores and decent hands-on ability can finish the first small part of the national final experimental questions without any problem.

The second part is a little more troublesome.

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

CPhO exams come and go, to put it bluntly, it is a test of theoretical knowledge.

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

This is the end of the experiment session.

Including Shen Qi, many contestants successfully completed the experiment and answered the questions.

The scores of the experimental questions will be announced on the same day.

None of the contestants got the full score of 80 points for the experimental questions, and the highest score was 79.5 points.

In the link of practical actions, each contestant was deducted more or less points.

There is no way to do it, and there is no standard posture in the actual exercise, and no one can guarantee that every detail of himself is perfect.

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

The experimental score came out, which means that the total score of this year's CPhO National Finals has 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 High School Attached to 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 (SAR Middle School), 348.5 points;

...

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

The total scores are only announced to the top 200, among which the top 50 will get the national first prize, 51-200 will get the national second prize, and 201-412 will get the third prize.

The national gold medal score line has been drawn to 282 points, which is the score of the player ranked 50th.

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

When the dust settled, 50 players won the first national gold medal, and the top 40 gold medalists were selected for the Wujing National Training Team.

As in previous years, the top 50 contestants are basically from domestic schools with strong physical and academic competitions.

Except for Shen Qi who is ranked number one.