Xueba, I beg you to go and escort him quickly!

"Show him!"

Wang Hanshan picked up his mobile phone and took a picture of the question.

When he was about to send it to Xu Heng, he realized that Xu Heng had sent him a message before.

"Any more?"

These three words are so dazzling and heartbreaking!

"hiss……!!!"

Wang Hanshan sent the topic over.

topic:

As shown in the figure, the distance between two identical long straight wires 1 and 2 placed vertically and parallelly is a (a << the length of the long straight wire), and there is a constant current with the same direction and magnitude in the two wires. direction up.

The positive ions in the wire are all stationary, and the charge amount of the positive ions in the wire per unit length is λ; the conduction electrons that form the current move down the wire at a speed V0 at a constant speed, and the charge amount of the conduction electrons in the wire per unit length is -λ.

Known: the charge per unit length is η...

……

Use the length contraction formula in special relativity to find the ratio of constant ke and km.

Tips: Ignore gravity; the electric charges of positive ions and electrons have nothing to do with the choice of inertial frame of reference; the speed of light in vacuum is c.

While Xu Heng was looking at the question, Wang Hanshan and the other three were also looking at it.

When they saw the "special theory of relativity", they were frightened silly.

"Professor! Professor! This, this problem, is it really something we can do? Special relativity!"

Fang Zhonggui looked at the three people whose facial features were distorted by shock, and nodded seriously.

"!!!"

Come on! ! !

The difficulty of this question is much more difficult than the one just now!

"This this this..."

Fang Zhonggui took a deep breath and got up slowly, "I'm going to the bathroom, you guys go back first! If he can do it, just tell me, if he can't, forget it."

"go Go!"

Fang Zhonggui couldn't wait any longer, left Wang Hanshan and the others aside, and went!

The restroom is on the same floor!

In addition, Fang Zhonggui was very anxious, so it was done in a few minutes!

From the time he went, to the time he came back, he met a teacher on the way, and the two chatted for a while, and it took less than 15 minutes...

But when he walked into the office, the three of Wang Hanshan didn't leave, they were all still there.

Fang Zhonggui, "Why are you still here?"

PS: Thanks [tail number 0862] [shu]

The fifth update, 2W+ words are here!Kneel for all support!

.

Chapter 166

Fang Zhonggui sat back at his desk and looked at Wang Hanshan and his three classmates.

"What happened to you?"

"Are you still struggling with that question?"

"To be honest, I was also very shocked when I first saw the answer, so it's understandable for you to be surprised, but... you can't keep being so surprised!"

"You must adjust your mentality, and you must correct yourself as soon as possible, so that you can..."

Just as he was talking, Wang Hanshan slowly said in a trembling voice, "c square..."

Fang Zhonggui, "What c square? What..."

"Cock!"

Suddenly, Fang Zhonggui came back to his senses, and he stood up abruptly again, "Ah! Medicine! My ~ medicine! Quick! Quick! Quick!"

"It's the third drawer on this side -! Quick!"

The three of Wang Hanshan immediately divided up the work, the one who took the medicine took the medicine, and the one who poured the water - poured the water.

"Professor! Slow down! Slow down!"

"Professor! Don't get excited! Don't get too excited!"

"Yes! Professor, your heart is not very good, you..."

Fang Zhonggui, "Is this something you can't be excited about! He actually figured it out!"

The three of Wang Hanshan frowned, exhausted all their strength, and asked, "So...Professor, the answer is really c squared?"

"hiss……"

Fang Zhonggui took a long breath, "Yes!"

Rumble!

!!!

Five thunders hit the top!

It's not just five thunders!

It's Bai Lei!

Qian Lei!

The three of Wang Hanshan's scalps felt numb.

They feel like their bodies are not their own!

"He actually figured it out!"

"My God! He gave the correct answer in such a short time before the professor went to the bathroom!"

"!!!!!!"

Fang Zhonggui glanced at the time.

"It's only 15 minutes!"

"Less than 15 minutes! What is the situation with this person!"

"Is he really just a sophomore in high school? Hiss!"

Fang Zhonggui, "!!!"

He looked at Wang Hanshan and the others.

Wang Hanshan and the others also looked at Fang Zhonggui.

"Professor... So, are you going to hire someone? Is this time short?"

Fang Zhonggui's scalp was numb, "Let me tell you the truth! The short time I just said was a few hours! Not ten minutes!"

The three of Wang Hanshan said, "!!!"

Fang Zhonggui took a deep breath again, "Call him! Quick! I want to hear the idea of ​​solving the problem."

Wang Hanshan immediately played the voice for Xu Heng.

pat!

Xu Heng refused, "I'm in class, it's inconvenient, what's the matter?"

Wang Hanshan, "Well, where's your train of thought? Do you only have one answer?"

Xu Heng, "Why don't I write it out for you...er...it might be a bit complicated...let's forget it! Wait for me to talk to you in the 10 minutes between classes!"

The corners of Wang Hanshan's eyes twitched fiercely, what can he do?He is also very helpless!

Can only wait!

"All right……"

that's it!

A professor of physics at Peking University, and three first-year students of Peking University, just guarded a mobile phone, waiting for Xu Heng for more than 30 minutes!

The moment Xu Heng's voice came over!

Wang Hanshan answered immediately.

Even Xu Heng was frightened.

Are you staying here?

Not even a second!

Pick up in seconds!

Xu Heng, "Uh..."

Fang Zhonggui and Wang Hanshan looked at each other.

Wang Hanshan said, "Student Xu Heng, tell me about it."

Xu Heng didn't ask whether it was right or wrong, he was very confident.

Straight to the point!

Xu Heng said bluntly: "In the reference frame S that is stationary relative to the positive ions, the positive ions in the wire do not move, and the conduction electrons move downward at a constant speed of V0..."

"..."

"In the first step, in the reference frame S', consider the magnitude and direction of the electric field force exerted by the wire 2 on the positive ions in the wire 1..."

"..."

"The second step..."

“这里是式子11，f’m+=qV0B’=（2kmqλV02）/（a根号下（1-V02/c2）。”

"..."

"The third step, in the reference frame S, consider the magnitude and direction of the electric field force and magnetic field force exerted by the wire 2 on the positive ions in the wire 1..."

"..."

"Because relative to the S system, the resultant force of other forces that may exist above should still be zero, and the positive ions are still in a state of uniform motion, so formula 16 should be equal to zero..."

"..."

"From formulas 8, 11 and 17, we can get ke/km=c2."

"Okay, it's that simple!"

"Class will start soon, I'm going to class, bye."

Hang up the phone with a snap.

Fang Zhonggui and Wang Hanshan were stunned.

Everyone's head was buzzing.

Nothing but a buzzing sound, a blank slate!

The four of them stared wide-eyed.

We looked at each other for a while in this office!

The whole office is silent!

at last!

Wang Hanshan broke the calm. He took a deep breath and said in a trembling voice, "Teach, professor..."