交流电桥原理与直流电桥相似,不同的是四臂上的元件不定是电阻,可以是R、L、C元件 图中已规定了电流方向和回路绕行方向以及电源的极性

根据交流元件的联结形式不同,也将交流电路区分为 简单交流电路与复杂交流电路。类似于直流电路,元件最 简单的联结方式为串联和并联,而凡是能够通过运用元件 串、并联的计算法将电路化为一个单回路的交流电路称为 简单交流电路;反之

一、各种形式的交流电 交流电路:如果电源电动势e(t)随时间作周期性变化,则 各段电路中的电压u(t)和电流i(t)均随时间作周期性变 化,这种电路叫做交流电路

Chapter 3 Kinematics I: rectilinear motion Motion implies change, and it is change make life-and physics-visible and interesting. Kinematics is the theory about the description of motion. Physical theories are creations of the human intellect; they must be invented rather than discovered

2.1 scalar and vector quantities 1. scalar Physical concepts that require only one numerical quantity for their complete specification are scalar quantities. 2. vector Vector quantities require for their complete specification a positive quantity, called the magnitude of the vector and the direction otice:Not all things with a magnitude and direction are vectors

1 Physics as Natural Philosophy Physics is one of the liberal arts, combining elements of reason, philosophy, mathematics, language, and rhetoric. The term natural philosophy reflects the creative and dynamic interplay that exists in physics among experiment, theory, logic, insight, inspiration, symmetry, beauty, and language

That streams of electrons possess the properties of beams of waves was dis- covered early in 1927 in a large industrial laboratory in the midst of a great city, and in a small university laboratory overlooking a cold and desolate sea. The coincidence seems the more striking when one remembers that facil- ities for making this discovery had been in constant use in laboratories throughout the world for more than a quarter of a century. And yet the coincidence was not, in fact, in any way remarkable. Discoveries in physics are made when the time for making them is ripe, and not before; the stage is set, the time is ripe, and the event occurs-more often than not at widely separated places at almost the same moment

When in 1920 I resumed my studies of theoretical physics which had long been interrupted by circumstances beyond my control, I was far from the idea that my studies would bring me several years later to receive such a higl and envied prize as that awarded by the Swedish Academy of Sciences each year to a scientist: the Nobel Prize for Physics. What at that time drew me towards theoretical physics was not the hope that such a high distinction

Nobel lecture december 12, 1933 On passing through an optical instrument, such as a telescope or a camera lens, a ray of light is subjec reflecting surface. The path of the rays can be constructed if we know the two simple laws which govern the changes in direction: the law of refrac- tion which was discovered by Snellius a few hundred years ago, and the law of reflection with which Archimedes was familiar more than 2,000 years ago

Nobel Lecture december 13. 1946 The history of the discovery of the exclusion principle m, for which I have received the honor of the Nobel Prize award in the year 1945, goes back to my students days in Munich. While, in school in Vienna, I had already ob- tained some knowledge of classical physics and the then new Einstein rel- ativity theory, it was at the University of Munich that I was introduced by Sommerfeld to the structure of the atom- somewhat strange from the point of view of classical physics. I was not spared the which every