# 物理代写|电动力学代写electromagnetism代考|Tagranoian Viewnoint

#### Doug I. Jones

Lorem ipsum dolor sit amet, cons the all tetur adiscing elit

couryes™为您提供可以保分的包课服务

couryes-lab™ 为您的留学生涯保驾护航 在代写电动力学electrodynamics方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写电动力学electrodynamics代写方面经验极为丰富，各种代写电动力学electrodynamics相关的作业也就用不着说。

## 物理代写|电动力学代写electromagnetism代考|Tagranoian Viewnoint

The nonrelativistic motion of a particle of mass $m$ moving in a potential $V(\mathbf{r}, t)$ is described by the Lagrangian
$$L=\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2-V(\mathbf{r}, t) .$$
Here, the independent variables are $\mathbf{r}$ and $t$, so that two kinds of variations can be considered. First, a particular motion is altered infinitesimally, that is, the path is changed by an amount $\delta \mathbf{r}$ :
$$\mathbf{r}(t) \rightarrow \mathbf{r}(t)+\delta \mathbf{r}(t) .$$
Second, the final and initial times can be altered infinitesimally, by $\delta t_1$ and $\delta t_2$, respectively. It is more convenient, however, to think of these time displacements as produced by a continuous variation of the time parameter, $\delta t(t)$,
$$t \rightarrow t+\delta t(t)$$
so chosen that, at the endpoints,
$$\delta t\left(t_1\right)=\delta t_1, \quad \delta t\left(t_2\right)=\delta t_2 .$$
The corresponding change in the time differential is
$$d t \rightarrow d(t+\delta t)=\left(1+\frac{d \delta t}{d t}\right) d t,$$
which implies the transformation of the time derivative,
$$\frac{d}{d t} \rightarrow\left(1-\frac{d \delta t}{d t}\right) \frac{d}{d t}$$
Because of this redefinition of the time variable, the limits of integration in the action,
$$W_{12}=\int_2^1\left[\frac{1}{2} m \frac{(d \mathbf{r})^2}{d t}-d t V\right]$$
are not changed, the time displacement being produced through $\delta t(t)$ subject to $(8.7)$. The resulting variation in the action is now
\begin{aligned} \delta W_{12} & =\int_2^1 d t\left{m \frac{d \mathbf{r}}{d t} \cdot \frac{d}{d t} \delta \mathbf{r}-\delta \mathbf{r} \cdot \nabla V-\frac{d \delta t}{d t}\left[\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right]-\delta t \frac{\partial}{\partial t} V\right} \ & =\int_2^1 d t\left{\frac{d}{d t}\left[m \frac{d \mathbf{r}}{d t} \cdot \delta \mathbf{r}-\left(\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right) \delta t\right]\right. \ & \left.+\delta \mathbf{r} \cdot\left[-m \frac{d^2}{d t^2} \mathbf{r}-\nabla V\right]+\delta t\left(\frac{d}{d t}\left[\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right]-\frac{\partial}{\partial t} V\right)\right},(8.11) \end{aligned}
where, in the last form, we have shifted the time derivatives in order to isolate $\delta \mathbf{r}$ and $\delta t$.

## 物理代写|电动力学代写electromagnetism代考|Hamiltonian Viewpoint

Using the above definition of the momentum, we can rewrite the Lagrangian as
$$L=\mathbf{p} \cdot \frac{d \mathbf{r}}{d t}-H(\mathbf{r}, \mathbf{p}, t),$$
where we have introduced the Hamiltonian
$$H=\frac{p^2}{2 m}+V(\mathbf{r}, t) .$$
We are here to regard $\mathbf{r}, \mathbf{p}$, and $t$ as independent variables in
$$W_{12}=\int_2^1[\mathbf{p} \cdot d \mathbf{r}-d t H] .$$
The change in the action, when $\mathbf{r}, \mathbf{p}$, and $t$ are all varied, is
\begin{aligned} \delta W_{12}= & \int_2^1 d t\left[\mathbf{p} \cdot \frac{d}{d t} \delta \mathbf{r}-\delta \mathbf{r} \cdot \frac{\partial H}{\partial \mathbf{r}}+\delta \mathbf{p} \cdot \frac{d \mathbf{r}}{d t}-\delta \mathbf{p} \cdot \frac{\partial H}{\partial \mathbf{p}}-\frac{d \delta t}{d t} H-\delta t \frac{\partial H}{\partial t}\right] \ = & \int_2^1 d t\left[\frac{d}{d t}(\mathbf{p} \cdot \delta \mathbf{r}-H \delta t)+\delta \mathbf{r} \cdot\left(-\frac{d \mathbf{p}}{d t}-\frac{\partial H}{\partial \mathbf{r}}\right)\right. \ & \left.+\delta \mathbf{p} \cdot\left(\frac{d \mathbf{r}}{d t}-\frac{\partial H}{\partial \mathbf{p}}\right)+\delta t\left(\frac{d H}{d t}-\frac{\partial H}{\partial t}\right)\right] . \end{aligned}
The action principle then implies
\begin{aligned} \frac{d \mathbf{r}}{d t} & =\frac{\partial H}{\partial \mathbf{p}}=\frac{\mathbf{p}}{m}, \ \frac{d \mathbf{p}}{d t} & =-\frac{\partial H}{\partial \mathbf{r}}=-\nabla V, \ \frac{d H}{d t} & =\frac{\partial H}{\partial t}, \ G & =\mathbf{p} \cdot \delta \mathbf{r}-H \delta t . \end{aligned}

# 电动力学代考

## 物理代写|电动力学代写electromagnetism代考|Tagranoian Viewnoint

$$L=\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2-V(\mathbf{r}, t) .$$

$$\mathbf{r}(t) \rightarrow \mathbf{r}(t)+\delta \mathbf{r}(t) .$$

$$t \rightarrow t+\delta t(t)$$

$$\delta t\left(t_1\right)=\delta t_1, \quad \delta t\left(t_2\right)=\delta t_2 .$$

$$d t \rightarrow d(t+\delta t)=\left(1+\frac{d \delta t}{d t}\right) d t,$$

$$\frac{d}{d t} \rightarrow\left(1-\frac{d \delta t}{d t}\right) \frac{d}{d t}$$

$$W_{12}=\int_2^1\left[\frac{1}{2} m \frac{(d \mathbf{r})^2}{d t}-d t V\right]$$

\begin{aligned} \delta W_{12} & =\int_2^1 d t\left{m \frac{d \mathbf{r}}{d t} \cdot \frac{d}{d t} \delta \mathbf{r}-\delta \mathbf{r} \cdot \nabla V-\frac{d \delta t}{d t}\left[\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right]-\delta t \frac{\partial}{\partial t} V\right} \ & =\int_2^1 d t\left{\frac{d}{d t}\left[m \frac{d \mathbf{r}}{d t} \cdot \delta \mathbf{r}-\left(\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right) \delta t\right]\right. \ & \left.+\delta \mathbf{r} \cdot\left[-m \frac{d^2}{d t^2} \mathbf{r}-\nabla V\right]+\delta t\left(\frac{d}{d t}\left[\frac{1}{2} m\left(\frac{d \mathbf{r}}{d t}\right)^2+V\right]-\frac{\partial}{\partial t} V\right)\right},(8.11) \end{aligned}

## 物理代写|电动力学代写electromagnetism代考|Hamiltonian Viewpoint

$$L=\mathbf{p} \cdot \frac{d \mathbf{r}}{d t}-H(\mathbf{r}, \mathbf{p}, t),$$

$$H=\frac{p^2}{2 m}+V(\mathbf{r}, t) .$$

$$W_{12}=\int_2^1[\mathbf{p} \cdot d \mathbf{r}-d t H] .$$

\begin{aligned} \delta W_{12}= & \int_2^1 d t\left[\mathbf{p} \cdot \frac{d}{d t} \delta \mathbf{r}-\delta \mathbf{r} \cdot \frac{\partial H}{\partial \mathbf{r}}+\delta \mathbf{p} \cdot \frac{d \mathbf{r}}{d t}-\delta \mathbf{p} \cdot \frac{\partial H}{\partial \mathbf{p}}-\frac{d \delta t}{d t} H-\delta t \frac{\partial H}{\partial t}\right] \ = & \int_2^1 d t\left[\frac{d}{d t}(\mathbf{p} \cdot \delta \mathbf{r}-H \delta t)+\delta \mathbf{r} \cdot\left(-\frac{d \mathbf{p}}{d t}-\frac{\partial H}{\partial \mathbf{r}}\right)\right. \ & \left.+\delta \mathbf{p} \cdot\left(\frac{d \mathbf{r}}{d t}-\frac{\partial H}{\partial \mathbf{p}}\right)+\delta t\left(\frac{d H}{d t}-\frac{\partial H}{\partial t}\right)\right] . \end{aligned}

\begin{aligned} \frac{d \mathbf{r}}{d t} & =\frac{\partial H}{\partial \mathbf{p}}=\frac{\mathbf{p}}{m}, \ \frac{d \mathbf{p}}{d t} & =-\frac{\partial H}{\partial \mathbf{r}}=-\nabla V, \ \frac{d H}{d t} & =\frac{\partial H}{\partial t}, \ G & =\mathbf{p} \cdot \delta \mathbf{r}-H \delta t . \end{aligned}

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

Days
Hours
Minutes
Seconds

# 15% OFF

## On All Tickets

Don’t hesitate and buy tickets today – All tickets are at a special price until 15.08.2021. Hope to see you there :)