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如何在箭头下方添加文字，并控制文字的字体大小？

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如何在箭头下方添加文字，并控制文字的字体大小？

这是我的图片，我想$\mathrm{E}_{app} \mathbf{e}_z$在底部箭头下面和箭头中央添加，并且想单独控制字体大小，该怎么办？ f2

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{positioning}

\tikzset{
  rednode/.style = { 
    circle,
    draw,
    fill=red!80,
    inner sep=0pt,
    minimum size=3.5mm,
},
  bluenode/.style = { 
    circle,
    draw,
    fill=blue!30,
    inner sep=0pt,
    minimum size=3.5mm,
}
}
\begin{document}


  \begin{tikzpicture}[x={(5cm,0)},y={(0,1cm)}]
    
    \def\a{1cm} %两粒子横坐标差
    
    \def\b{2cm} %两倍
    \def\c{3cm} %三倍
    \def\e{4cm} %四倍
    \def\f{5cm}%五倍
    \def\g{6cm}%六倍
    \def\L{1.25cm}%电场线长
    \def\ha{0.25cm} %矩形边长的一半
    \def\H{2.3cm} %矩形高一半 
    % 电场线
    \draw [-stealth](-0.5cm-\L,\a) -- (-0.5cm,\a);
    \draw [-stealth](-0.5cm-\L,0) -- (-0.5cm,0);
    \draw [-stealth](-0.5cm-\L,-\a) -- (-0.5cm,-\a) node [below] {$\mathrm{E}_{app} \mathbf{e}_z$};
    
    %左矩形 
    \draw[dashed] (-\ha,\H) -- (\ha,\H); 
    \draw[dashed] (\ha,\H) -- (\ha,-\H);
    \draw[dashed] (\ha,-\H)--(-\ha,-\H);
    \draw[dashed] (-\ha,-\H)--(-\ha,\H);
    %右矩形
     \draw[dashed] (-\ha+\g,\H) -- (\ha+\g,\H); 
     \draw[dashed] (\ha+\g,\H) -- (\ha+\g,-\H);
     \draw[dashed] (\ha+\g,-\H)--(-\ha+\g,-\H);
     \draw[dashed] (-\ha+\g,-\H)--(-\ha+\g,\H);   
    

    % 带电粒子
    \node[bluenode](11) at (0,\b-0.3cm){$-$};
    \node[bluenode](12) at (0,-\b+0.3cm){$-$};
    \node[bluenode](21) at (\a,\b-0.1cm){$-$};
    \node[rednode](22) at (\a,0.5cm){$+$};\draw (11)--(22);
    \node[bluenode](23) at (\a,-\b+1.2cm){$-$};
    \node[rednode](24) at (\a,-\b+0.2cm){$+$};\draw (12)--(24);
    \node[rednode](31) at (\b,\b+0.1cm){$+$};\draw (21) -- (31);
    \node[bluenode](32) at (\b,0.7cm){$-$};
    \node[bluenode](33) at (\b,-0.1cm){$-$};
    \node[rednode](34) at (\b,-\b+0.6cm){$+$};\draw (23) -- (34);
    \node[rednode](41) at (\c,\b-0.5cm){$+$};\draw(32) -- (41);
    \node[bluenode](42) at (\c,0.5cm){$-$};
    \node[rednode](43) at (\c,-\b+0.7cm){$+$};\draw(33) -- (43);
    \node[bluenode](44) at (\c,-\b+0.1cm){$-$};
    \node[rednode](51) at (\e,\b-0.15cm){$+$};\draw(42) -- (51);
    \node[bluenode](52) at (\e,0.3cm){$-$};
    \node[rednode](53) at (\e,-0.8cm){$+$};\draw(44) -- (53);
    \node[bluenode](54) at (\e,-\b+0.1cm){$-$};
    \node[bluenode](61) at (\f,\b){$-$};
    \node[rednode](62) at (\f, 0.7cm){$+$};\draw(52) -- (62);
    \node[bluenode](63) at (\f,-0.6cm){$-$};
    \node[rednode](64) at (\f,-\b+0.2cm){$+$};\draw(54) -- (64);
    \node[rednode](71) at (\g, 1cm){$+$};\draw(61) -- (71);  
    \node[rednode](72) at (\g, -0.6cm){$+$};\draw(63) -- (72);  
  \end{tikzpicture}
\end{document}

我的代码很麻烦，我非常乐意听到其他关于我的代码的建议。

答案1

改编

  • 减少各处的冗余代码
    • 例如定义basenode由rednode和使用bluenode
  • 使用有意义的变量
  • 写英文注释，以便其他人能够理解（尤其是变量）
  • 定义命令\drawchargepair以简化电荷放置
  • 用于\foreach箭
  • 使用定义大小的节点绘制虚线矩形
  • 如果这是主要尺度，则使用mm而不是（写起来比或更短）cm5mm0.5cm.5cm
  • （在这个例子中，我减少了电荷对的数量）

结果

在此处输入图片描述

代码

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{positioning}

\tikzset{
    basenode/.style = {
        circle,
        draw,
        inner sep=0pt,
        minimum size=3.5mm,
    },
    rednode/.style = { 
        basenode,
        fill=red!80,
    },
    bluenode/.style = { 
        basenode,
        fill=blue!30,
    },
    myrect/.style = {
        draw,
        dashed,
        minimum width=5mm,
        minimum height=46mm,
    },
}

\begin{document}

\NewDocumentCommand{\drawchargepair}{ r() r() }{
    % draws two connected charges
    % (#1) position of - charge
    % (#2) relative position of + charge
    \draw (#1) node[bluenode]{$-$} -- ++(#2) node[rednode]{$+$};
}

\begin{tikzpicture}[x={(5cm,0)},y={(0,1cm)}]
    \def\arrowLength{1.25cm}
    
    % input arrows
    \foreach \i in {-1, 0, 1} {
        \draw [-stealth](-5mm-\arrowLength,\i*10mm) -- ++(\arrowLength,0);
    }
    \node[below] at (-5mm-.5*\arrowLength,-10mm) {$\mathrm{E}_{\text{app}} \mathbf{e}_z$};
    
    % rectangles
    \node[myrect] at (0,0) {};
    \node[myrect] at (60mm,0) {};
    
    % charge pairs
    \drawchargepair (0,17mm) (10mm,-10mm)
    \drawchargepair (0,-17mm) (10mm,-1mm)
    \drawchargepair (10mm,19mm) (10mm,2mm)
\end{tikzpicture}

\end{document}

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