234 years ago today, on September 22, 1791 (August 25, 1791 lunar calendar), the British physicist and chemist Faraday was born. The unit of capacitance in electricity is called "farad". Why is it "farad"? This is in honor of the famous chemist and physicist Faraday's great contribution to electricity. Faraday was a poor child since childhood. Born on September 22, 1791, his father was a blacksmith. Due to his poor family, Faraday only read a few enlightenment books from an early age. At the age of 13, he was a newsboy, and Lebo, the bookseller, saw that he was smart and diligent, and recruited him into the nail bookstore as an apprentice. The books in the staple shop were piled up, and Faraday read all kinds of books like hunger and thirst in his spare time. The articles on electricity in the Encyclopedia Britannica gave him a strong interest in natural science. He used waste materials to make electrostatic motors, conducted simple chemistry and physics experiments, and used his spare time to listen to scientific lectures. A patron of Lippo praised Faraday's studious spirit and gave him a ticket to the Royal Academy, which gave him the opportunity to listen to the famous chemist David's lectures. He recorded all of David's lectures and went back to study further. In 1812, Faraday's apprenticeship expired and he was introduced to David as a temporary scribe. David read Faraday's lecture notes and was very impressed, so he hired him as a laboratory assistant. From then on, Faraday began his scientific career. In the autumn of 1813, David married a wealthy young widow and decided to go on a honeymoon trip to Europe. The housekeeper and servants were fired because they knew that the widow was pampered and willful and would not follow. In this way, Faraday combined the three positions of assistant, housekeeper, and servant to accompany David on his travels. He worked for his master during the day, and at night when his master rested, he read and experimented. This trip saw many famous scientists, participated in various academic exchanges, and learned French and Italian, which greatly broadened his horizons. As a good friend of Faraday's put it: "He [Faraday] went to university in Europe, and his examiners were the masters he served, and the celebrities who came in David's name." When Faraday returned home in April 1815, he immediately devoted himself to scientific research. He conducted various experiments boldly, sometimes risking his life. On one occasion, he experimented with chlorine gas, knowing that it was toxic, and inhaled it himself to verify its properties. This spirit of risk-taking and diligence led to a series of rapid scientific achievements. In 1816, he published his first scientific paper; in 1818, he studied alloy steel and found that the addition of trace metal elements could affect the properties of steel. In 1820, he first used a displacement reaction to make two carbon chlorides; in 1823, he liquefied chlorine gas; in 1825, he separated benzene from petroleum and tried to make chemical glass; in 1824, he was elected to the Royal Society at the age of 33; the following year, he was promoted to the director of the laboratory of the Royal Academy. After years of repeated experiments, he finally announced on October 17, 1831 that he could use permanent magnets to generate electricity, which is known as the principle of electromagnetic induction. Using this principle, he created the world's first induction generator. Faraday's motto was: "As a candle illuminates a man, there is a little heat and a little light, and he faithfully and surely contributes his strength to the great cause of mankind." Indeed, there was not a day in his life that he did not contribute to mankind until August 25, 1867, when he died peacefully in his work chair.