Chapter 544 253 Lift, It Can All Be Lifted (8.2K)_4

"Stimulated in the presence of light—or in other words, the equilibrium junction is disrupted, leading to a potential difference?"

"But in this case, the actual environment of stimulation might be invisible to the naked eye..."

Watching Old Fa talk eloquently, Xu Yun remained silent.

However, his tightly clasped hands indicated that his heart was not calm at the moment.

As everyone knows.

The essence of the photovoltaic phenomenon comes down to the atomic energy band structure, involving the concepts of valence band and conduction band.

The so-called valence band refers to the region relatively close to the atomic nucleus.

The electrons here are tightly held and cannot easily escape.

The conduction band, on the other hand, is the region far from the atomic nucleus, where electrons are unregulated and relatively free.

If an external electric field sets these electrons in motion, the material conducts electricity.

Apart from these two regions, there is another area above the valence band and below the conduction band.

This area is where electrons are not allowed to exist, known as the forbidden band.

So, in the natural world, there are generally two distinctly different materials:

One with a very narrow forbidden band, or no forbidden band at all.

At room temperature, the outer electrons of its valence band can easily transition to the conduction band.

This is a conductor.

Conversely, if the material has a wide forbidden band, generally greater than three electron volts, the electrons at room temperature will obediently stay in the valence band, making it unable to conduct electricity.

This is an insulator.

Materials with an energy gap less than 3eV between the valence and conduction bands are semiconductors.

These electrons will form something called a PN junction, exhibiting different electrical properties at each end, thereby forming an electric field pointing from N to P.

This electric field forms spontaneously, thus also known as the built-in electric field of the conductor.

As for the role of the photovoltaic effect, it is to once again "tempt" those already paired valence band electrons.

That is, the valence band electrons absorb the energy of light, increase in energy, and transition to the conduction band.

The holes left by the electrons are affected by the built-in electric field and get thrown to both sides, forming an electric field pointing from P to N.

This is the photoelectric field, opposite in direction to the built-in electric field.

At this point, as long as an external circuit is connected, due to the existence of a potential difference, current will be generated in the circuit.

This is also the principle of photovoltaic power generation in later times, except the utilization rate has always been low, so it is still a developing project.

The 1850 era where Old Fa and the others live is far from discovering electrons, with Coulomb only proposing the concept of charge, and a long way off from actual particles.

Yet Old Fa can associate phenomena with the internal 'junction', which is truly astonishing, isn't it?

In fact.

This is not Xu Yun's first encounter with such a situation.

Little Niu calculating infinitesimals in the 1665 instance...

Old Jia deriving curvature in the 1100 instance...

Old Su creating self-priming pumps with primitive knowledge.....

In front of these giants of human history, Xu Yun always feels his own insignificance.

Compared to these true sages, he is merely a lucky man with a special halo, and he has a long, long way to go.

.....

Just as Xu Yun was reflecting in his heart, Thomson quickly walked over from the side:

"Luo Feng, the other set of equipment you wanted is ready."

Xu Yun snapped back to reality.

He first glanced at Angus Roman in the distance.

Tsk tsk, this villain is actually speechless this time; I was still waiting to put him in his place again...

Then he cleared his throat, dismissing this boring thought, and said to Old Fa:

"Mr. Faraday, are you ready?"

Old Fa was still deep in thought about the photovoltaic effect, and upon hearing this, instinctively paused:

"Uh, ready for what?"

Xu Yun gave him a mysterious smile and glanced into the distance:

"Of course, to prepare....."

"To topple the foundations of the physics edifice!"

........

Note:

Yesterday a student asked why there were dashboards in this era. Is it possible that the first train invented in 1804 already had a dashboard.....

Pierre Curie was hit by a carriage on the road and died on the spot. Madam Curie, after a few years of widowhood, got together with student Lang Zhiwan. It's human nature to form another family after a spouse's death, let alone that Madam Curie wasn't seamless, the shortest was over three years. However, since Lang Zhiwan was a married man at the time, their love story was clouded with controversy. On November 7, 1911, Reuters reported that year's Nobel Prize in Chemistry would be awarded to Madam Curie. As a result, on November 23, Mrs. Lang Zhiwan, through her brother, published Madam Curie's love letter to Lang Zhiwan in the newspaper. Since then, Gaul's newspapers began to extensively report on Madam Curie's "mysterious romance" with Lang Zhiwan and started to publish her letters in large numbers. Some Gauls even attacked her residence, smashing her windows with stones. A group of scientists in Gaul who originally supported Madam Curie also began to change their stance, writing joint letters asking Marie to leave France, leading Madam Curie to ultimately fail to be selected as an academician of the Gaul Academy of Sciences and escape to a monastery within Gaul for 14 months to let the storm pass. The derogatory term 'Polish Whore' appeared at that time. Here's a cheeky little episode. After Lang Zhiwan separated from Madam Curie, his wife agreed that Lang Zhiwan could publicly have a mistress other than Madam Curie as a condition to salvage their failed marriage. Years later, to support his lover, Lang Zhiwan shamelessly asked Madam Curie to arrange a position for this female student at the research institute... (CNKI:SUN:KXSJ.0.2014-07-019) Oddities occur every year, especially in the early 20th century.