{"resolved":true,"match_type":"uuid","source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","requested_by":"printed_page","book":{"source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","id":"38270854-596f-4a26-8183-db8c968c6020","uuid":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","normalized_title":"编码隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","isbns":["9787121181184","0123456789","6044921875","3039331000","0000000000","0000000000000"],"parsed":true,"ai_readable":true,"document_type":"book","page_count":438,"navigation_url":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020","title_url":"https://workshop.closeclaw.top/ai/title/%E7%BC%96%E7%A0%81%20%E9%9A%90%E5%8C%BF%E5%9C%A8%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%BD%AF%E7%A1%AC%E4%BB%B6%E8%83%8C%E5%90%8E%E7%9A%84%E8%AF%AD%E8%A8%80","fixed_page_url_template":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","path_api_url_template":"https://workshop.closeclaw.top/api/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","read_url":"https://workshop.closeclaw.top/api/ai/read/38270854-596f-4a26-8183-db8c968c6020","page_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/page","search_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/search"},"page":{"printed_page":30,"pdf_page":46,"physical_index":46,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"f12bdaa00bf1799dbd4e0d2af51974f8ba3036a3d0d5ac4e2072d2994c07c335"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"上图中的那段折线对于电气工程师来说是表示电阻的符号。这里我们用它来表示电路中的电阻既不很小也不很大。\n\n如果导线电阻较低的话，它将变热并且发光。这就是白炽灯发光的原理。通常，白炽灯泡公认的发明者是美国著名发明家，托马斯·阿尔瓦·爱迪生(ThomasAlvaEdison，1847-1931），但是这种观点是在他取得灯泡的专利之后（1879）被广为传播的，实际上在这个领域很多科学家都有过研究。\n\n灯泡里面有一根很细的金属丝，我们称它为灯丝，一般情况下灯丝是用钨制作的。灯丝的一端连在灯泡底座的凸起上，另一端连到金属底座上，金属底座与凸起之间被绝缘层隔开。金属丝的电阻使它开始发热。如果暴露在空气中，钨丝将达到燃点并开始燃烧，但是在灯泡的真空泡室内，钨丝就会发出光亮。\n\n大多数普通手电筒都用2节电池串联成一组，总的电压是3伏。手电筒中一般使用电阻为4欧的灯泡。因此，电流的大小等于3伏除以4欧，也就是0.75安，也可以写成750毫安。这意味着每秒钟有4,680,000,000,000,000,000个电子流经灯泡（如果使用欧姆表对手电筒灯泡的电阻进行实际测量，你将得到一个远远小于4欧的读数。这是因为钨的阻抗与它的温度有关，当灯泡温度升高并开始发光时，钨丝的阻抗也随之增加)。\n\n你或许已经发现，买回家的灯泡上都标有一个固定的瓦特数。瓦特这个单位得名于詹姆斯·瓦特(JamesWatt，1736-1819)，他以对蒸汽机的研究而广为人知。瓦特是功率（P）的计量单位，它的计算公式如下：\n\n$$\nP = E \\ \\times \\ I\n$$\n\n我们的手电筒是3伏，0.75安的，这表明灯泡的功率应该是2.25瓦特。\n\n编码——隐匿在计算机软硬件背后的语言\n\n30","previous_page":29,"next_page":31}