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答案1
拖延模式全力开启……
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[scale=2.5,>=latex,font=\scriptsize]
\draw[thick](0,0)circle(1);
\draw(0,1.5)node[above]{$+Q$ (var)}--(0,-1.5)node[below]{$-Q$ (var)} ;
\draw(-1.5,0)node[above]{$-P$ (W)}node[below]{(Input)}--(1.5,0)node[above]{$+P$ (W)}node[below]{(Output)};
\draw[thick,->](0,0)--node[fill=white]{(Capacitive)}(45:1)node[above right]{$S$ (VA)};
\node at (135:.5){(Capacitive)};
\node at (-45:.5){(Inductive)};
\node at (-135:.5){(Inductive)};
\fill(1,0)circle(1pt)node[below left,fill=white,outer sep=4pt]{Rated $P$};
\fill(0,1)circle(1pt)node[above,fill=white,outer sep=4pt]{Rated $Q$};
\fill(-1,0)circle(1pt) (0,-1)circle(1pt) ;
\end{tikzpicture}
\begin{tikzpicture}[scale=2.5,>=latex,font=\scriptsize]
\draw[thick,gray,dashed](45:1)arc(45:135:1) (225:1)arc(225:315:1);
\draw[thick](-45:1)arc(-45:45:1)--(135:1)arc(135:225:1)--cycle;
\draw(0,1.5)node[above]{$+Q$ (var)}--(0,-1.5)node[below]{$-Q$ (var)} ;
\draw(-1.5,0)node[above]{$-P$ (W)}node[below]{(Input)}--(1.5,0)node[above]{$+P$ (W)}node[below]{(Output)};
\draw[thick,->](0,0)--node[fill=white]{(Capacitive)}(45:1)node[above right]{$S$ (VA)};
\node at (135:.5){(Capacitive)};
\node at (-45:.5){(Inductive)};
\node at (-135:.5){(Inductive)};
\fill(1,0)circle(1pt)node[below left,fill=white,outer sep=4pt]{Rated $P$};
\fill(0,1)circle(1pt)node[above,fill=white,outer sep=4pt]{Rated $Q$};
\fill(-1,0)circle(1pt) (0,-1)circle(1pt) ;
\end{tikzpicture}
\end{document}