感生电动势及动生电动势表达式与E=-(dΦ/dt)的等价性讨论

用微分法则和矢量代数由Ｅ＝－ｄΦｄｔ在一定条件下直接导出感生电动势和动生电动势表达式,说明其具有等价性     

几种电动势的分析

电动势是一个既重要又抽象的物理量，教材中有四处论述到它，即电池的电动势，导体切割磁感线运动产生的动生电动势和磁通量变化所产生的感生电动势，以及自感电动势，本文就上述四种电动势进行具体分析。     

动生、感生电动势与法拉第电磁感应定律

从法拉第电磁感应定律出发证明了闭合线圈的感应电动势是感生电动势与动生电动势之和     

物理竞赛中使用积分法求解感应电动势一二

为提升物理竞赛中学生运用积分法解决物理问题的能力, 以感应电动势的求解为例, 提出了用积分法 解题的一般思路. 对于动生电动势, 先寻找动生电动势微元, 再通过对微元积分求解; 对于感生电动势, 在已知感生 电场表达式时, 先求出感生电动势微元, 再对微元积分求解, 也可先利用积分求出通过回路的磁通量, 再根据法拉 第电磁感应定律求解     

关于动生电动势和感生电动势的讨论

通过两道例题对动生电动势的概念, 以及对电磁感应定律、 动生电动势和感生电动势的等效性进行了 讨论     

计算感生电动势的角度法

局限于圆柱形空间、方向平行于圆柱轴线的均匀磁场随时间均匀变化时，在周围空间激发感生电场。处于该电场中的有限长直导线上产生的感生电动势可由简捷方法求出。本文根据电动势的定义导出计算直导线上感生电动势的角度法。     

关于动生电动势起源的讨论

法拉第电磁感应定律统一描写了两种不同的物理现象：(1)曲面内磁通变化在构成曲面边界的闭合曲线上存在感应电动势；(2)在磁场中运动的曲线上存在动生电动势。虽然都知道这两个现象背后的基本规律均为麦克斯韦方程组和洛伦兹力公式，但是对现象(2)有不同的解释。本文从电荷轨道约束的角度讨论动生电动势的意义。对运动电荷的轨道进行约束需要对电荷施加一定的约束力。若预定轨道依赖于时间，约束力会对电荷作功，从而导致动生电动势，磁场在其中起着传递约束力的作用。我们通常不知道约束力的准确表达式。动生电动势的主要用处是让我们在分析电荷沿预定轨道运动的能量变化时无需求助于约束力，而这严格来说仅适用于准静态过程。电动势概念从准静态过程到迅变过程的推广并不唯一。本文把电动势一般地定义为：在单位正电荷瞬间走过某预定轨道的虚过程中外界对该电荷所作的虚功。这个定义同时适用于感应电动势和动生电动势，预定轨道曲线可以具有任意形状(开或闭合)并随时间变化。     

关于“感生电动势与动生电动势”教学的若干分析与建议

"感生电动势与动生电动势"的教学存在一定困难,针对教学的难点,进行了分析并提出建议.     

产生感应电动势条件的实验探究

主要是通过物理实验来探究“法拉第电磁感应定律”中产生感应电动势的条件.“只要电路的磁通量发生变化就会产生感应电动势”,无论电路是否闭合.教材直接给出结论没有给出过程.文中提供了3种方法来探究,并进行对比分析各种方法的优缺点.     

关于感生电动势计算问题的分析

产生感生电动势的非静电力为感生电场力, 它是感生电场对电荷的作用力, 而感生电场及非闭合回路 感生电动势的计算是大学物理中较难理解的问题. 通过对一道计算感生电动势的问题进行分析, 得到了3种解决问 题的方法, 加深了学生对感生电场及感生电动势计算的理解和掌握     

用板式电势差计测量电池的电动势和内阻实验的改进

分析了在“用板式电势差计测量电池的电动势和内阻”实验中 ,由于待测干电池的电动势和内阻在实验过程中均不为恒定值而引起的误差 ,依据电化学理论和电阻构成解释了实验现象 ,并给出了实验改进方案 .     

横向磁场中超导体感应电动势的计算

本文利用超导经典电磁理论，导出了超导体在横向磁场中切割磁感应线时感应电动势的计算公式，结果表明，与计算通常导体感应电动势的公式相同．     

用坡印亭矢量解释长直螺线管自感与互感电动势的产生

本文从坡印亭矢量出发，导出了自感电动势和互感电动势．     

Magnetoresonance EMF in thin manganite films

The effect of magnetoresonance emf (MREMF) in thin epitaxial films of rare-earth manganites La_0.67Sr_0.33MnO₃ is detected and investigated. The effect is manifested in the occurrence of a constant voltage under the action of microwave pumping in magnetic fields corresponding to ferromagnetic resonance conditions. The MREMF signal includes symmetric and antisymmetric components and changes its polarity upon switching of the external magnetic field. The temperature dependence of the effect (including the range in the neighborhood of the phase transition) is analyzed. The experimental data including the shape of the signal and its dependence of the field orientation are in good agreement with the results obtained in the theoretical model based on the mechanism of anisotropic magnetoresistance. It is shown that the magnetoresistance anisotropy in the manganite under investigation is negative and sharply attenuates as the temperature approaches the Curie point, almost vanishing in the paramagnetic phase.     

补偿法测电池电动势及内阻实验不确定度估算

用补偿法测电池电动势及内阻 ,并进行不确定度的估算。     

自感系数的两种定义并非无条件的等效

本文讨论了《大学物理》中自感系数的两种定义等效的条件．     

THz/sub-THz bolometer based on electron heating in a semiconductor waveguide

Direct detection THz/sub-THz bolometer is proposed. In it an electromagnetic wave propagates in the bipolar semiconductor waveguide, heats electrons and holes there, and therefore creates their bipolar thermodiffusion flow and, as well as, the electromotive force (emf). The flow causes the carrier excess concentration. Both this concentration and emf are used to get the bolometer response voltage. The bolometer theoretical model is developed. The possibility without cooling or moderate cooling (about 100 K for the Cd_0.2Hg_0.8Te bolometers) to get acceptable for applications values of the noise equivalent power is shown. Experimental results confirm the main model conclusions.     

The Difference Between the Standard and The Lorentz Transformations of the Electric and the Magnetic Fields

In this paper it is shown by using the Clifford algebra formalism that the usual Lorentz transformations of the three-dimensional (3D) vectors of the electric and magnetic fields E and B (which will be named as standard transformations (ST)) are different than the Lorentz transformations (LT) of well-defined quantities from the 4D spacetime. This difference between the ST and the LT is obtained regardless of the used algebraic objects (1-vectors or bivectors) for the representation of the electric and magnetic fields in the usual observer dependent decompositions of F. The LT correctly transform the whole 4D quantity, e.g., E_f : F · γ₀, whereas the ST are the result of the application of the LT only to the part of E_f, i.e., to F, but leaving γ₀ unchanged. The new decompositions of F in terms of 4D quantities that are defined without reference frames, i.e., the absolute quantities, are introduced and discussed. It is shown that the LT of the 4D quantities representing electric and magnetic fields correctly describe the motional electromotive force (emf) for all relatively moving inertial observers, whereas it is not the case with the ST of the 3D E and B.     

Induction and removal of thermal emf during static and alternating twisting

Polycrystalline copper wires and tubes were plastically deformed in unidirectional and alternating twisting, and the induced thermal emf was determined. As the relative shear increases during unidirectional twisting, the thermal emf increases, passing through three stages analogous to the stages of hardening. A change in the sense of the deformation in any of the stages is accompanied by a corresponding removal of the thermal emf and the subsequent restoration of this emf to the value corresponding to the unidirectional twisting. Five stages were found in the increase of the thermal emf. The effects of the grain size and the deformation rate on the magnitude of the induced thermal emf were determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 3, pp. 79–83, March, 1971.     

Effect of plastic deformation and quenching on the absolute thermal emf of nickel

The effect of the degree and rate of plastic deformation of nickel on the change of its absolute thermal emf was studied. The dynamic effect of the change of thermal emf was established, the dynamic coefficient being 1.22–1.25. Plastic deformation of quenched nickel reduced its absolute thermal emf, on the basis of which conclusions are drawn about the contributions, different in sign, of holes and dislocations to the change of the absolute thermal emf of nickel. The kinetics were studied of the recovery of the thermal emf induced in nickel by plastic deformation, and the existence was established of two stages of recovery, differing in nature and with different activation energies, 0.1 and 0.3 eV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 77–81, June, 1971.