The Shadow of Great Britain-Chapter 49 - 11 Electromagnetic Induction
49: Chapter 11 Electromagnetic Induction
49 -11 Electromagnetic Induction
All eyes converged on the podium as everyone was eager to see what kind of results could make the normally calm and composed Mr.
Michael Faraday so delighted.
Faraday said with a smile, “I believe many in the audience are aware that the world has been researching electricity and magnetism for many years now.
But in the earliest days, researchers thought these were two separate disciplines.”
However, the merchants disagreed with us.
Because in the 18th century, a London merchant made a startling discovery: his box of iron spoons had become surprisingly magnetic after being struck by lightning.
This disagreement between scientists and merchants wasn’t resolved until 1820, the year when Danish scientist Hans Oersted conducted an experiment.
He placed a wire parallel to a magnetic needle, and the moment he switched on the electric current, he was surprised to find that the needle jerked.
After repeated experiments, Oersted confirmed this was no coincidence.
Soon, he published a paper entitled ‘Experiments on the Effect of a Current of Electricity on the Magnetic Needle,’ and the scientific community called this great discovery ‘the magnetic effect of electric current.’
From then on, we who are but shallow researchers finally realized that electricity can indeed produce magnetism.
And when I was commanded by my mentor, Humphry Davy, to switch to the field of electrical research, my first thought was—if electricity can produce magnetism, could magnetism possibly produce electricity?
For this hypothesis, I conducted countless experiments over the years, and at long last, I recently obtained a staggering answer.
Electricity can produce magnetism, and magnetism can indeed produce electricity.
Electricity and magnetism are not separate disciplines, but rather a unified field with a strong correlation!”
With that, Faraday removed the black cloth covering the experimental table.
What appeared before everyone was a six-inch iron ring tightly wrapped with white cloth, with insulated copper wires wrapped around the left and right halves of the ring, respectively.
The copper wire on the left half was connected to a set of handmade batteries, forming an independent circuit.
The copper wire on the right half, however, was only connected to an ammeter.
Faraday introduced it enthusiastically, “As you can see, these two circuits are independent, not connected.
We call the circuit with the battery on the left Circuit A, and the one on the right without a battery but connected to an ammeter, Circuit B.
Therefore, according to our common sense, even if we supply electricity to Circuit A, the needle of the ammeter in Circuit B should not deflect.
But is this really the case?”
Faraday walked forward with a smile and gently flipped the switch for Circuit A.
Under the watchful eyes of all present, everyone noticed that the ammeter needle in Circuit B actually shifted slightly clockwise, but quickly returned to its original position.
And when Faraday turned off the switch, the ammeter needle actually deflected in the counterclockwise direction.
“My God!”
“What’s going on?”
Someone exclaimed, “Mr.
Faraday, are you sure you didn’t shake the table?”
Faraday spoke with a hint of humor, “Although the Royal Society has always been short of funds, we are not so poor as to not afford a proper experimental table.
If you don’t believe me, you can try it yourself.
Now, I will remove my hands from the table.”
He invited the gentleman who had raised the question to the stage, and after the man had tried seven or eight times and carefully examined the experimental table, he then exclaimed in admiration.
“Although I know your lectures are always spectacular, this one is undoubtedly the best ever!
Please allow me to represent the audience here and extend to you, once again, our highest respect.”
With that, the gentleman took off his hat, placed one hand on his chest, and bowed slightly.
The audience erupted into prolonged applause once again.
Just then, another gentleman stood up in the lecture seats.
He questioned, “Mr.
Faraday, I mean no offense.
But could it be that the iron ring used in your experiment is leaking electricity?
After all, both circuits are connected to the iron ring, and although you have insulated it with white cloth, perhaps there is still some current running through the ring.”
Faraday, upon hearing this question, didn’t give a direct answer but smiled and said, “In that case, please observe the second experiment.” fɾēewebnσveℓ.com
With that, he uncovered another black cloth from a table of experiments.
This time, the experimental apparatus was much simpler, consisting of only an ammeter, a hollow coil wrapped in copper wire, and two pieces of copper wire connecting both.
Faraday fished a magnet out of his pocket and placed it into the hollow coil.
As soon as the magnet flashed through the coil and fell onto the table, the ammeter needle also deflected.
Faraday smiled and said, “Sir, you see.
This time, I didn’t even use a battery.”
The audience present couldn’t help but exclaim, “God!
This could be the greatest discovery of the year!”
“Mr.
Faraday, by unifying electricity and magnetism, you might stand shoulder to shoulder with Sir Isaac Newton for this achievement.”
To the audience’s adulation, Faraday merely nodded in acknowledgment.
His face was radiant with a bright smile; although he was pleased that his academic accomplishments were recognized, he hadn’t forgotten his mission.
Doing an experiment was only the first step; the most important part was to gain experience from the experiment, summarize it into a conclusive principle that could be repeatedly verified, and explain the reasons and analyze the processes that caused these phenomena.
Eld, sitting in the audience, watched Faraday perform his experiments as if doing magic and listened to him talk about something called magnetic field lines.
He only felt dizzy and couldn’t understand a thing.
He nudged Arthur next to him with his elbow and whispered, “Do you understand this?”
Arthur raised his eyebrows and winked at him, “Somewhat.
To be honest, this is actually my second time listening.”
“Ah?
You attended the lecture secretly before?
Why didn’t you tell me?
Nevermind, explain to me this mess about magnetic field lines and how to discern the directions of the electric current and magnetic field.
This stuff is too hard.
I finally come to a lecture and must learn something.
Otherwise, when I chat with those lovely ladies who like science, I won’t know what to say.”
Arthur said, “Let me teach you an easy mnemonic.”
Eld asked curiously, “An easy method?”
Arthur began, “If you want to discern the direction of the current, then extend your right hand.
Put your four fingers together, keeping your thumb perpendicular to the other four fingers.
Yes, just like that, keep all five fingers in one plane.
Next, position the palm of your hand toward the N pole of the magnetic field, your thumb in the direction the conductor moves, which is the direction the magnet falls.
Then, the direction your remaining four fingers point is the direction of the induced current.”
Astonished, Eld exclaimed, “Arthur!
You’re a genius!
How did you come up with this method?”
Arthur sidestepped the question: “Do you still want to learn how to determine the direction of the force on a conductor?”
“Of course, I want to learn!”
“Then shut up and extend your left hand.”
“Oh?
It’s the left hand this time?”
“Quit the chatter and listen to me…”
Before Arthur could finish speaking, a gentle inquiring voice suddenly reached his ears.
“Excuse me, what are you talking about there?”
Arthur turned his head and saw that Faraday had somehow approached him and Eld.
The two unremarkable lads suddenly became the center of attention in the room.
Faraday kindly smiled and said, “Officer, could you please repeat the part about the right hand?
I only heard half of it.
As for the left hand, we can talk about that later.”
