说明文阅读——电路

火(huo)车走的(de)路(lu)叫(jiao)铁(tie)路(lu)，汽车走的(de)路(lu)叫(jiao)公路(lu)。同样，输送电(dian)(dian)(dian)流(liu)线路(lu)叫(jiao)电(dian)(dian)(dian)路(lu)。电(dian)(dian)(dian)路(lu)通常(chang)由四个部分组成，即(ji)电(dian)(dian)(dian)源、导线、电(dian)(dian)(dian)器和开关。例如(ru)手电(dian)(dian)(dian)筒电(dian)(dian)(dian)路(lu)，电(dian)(dian)(dian)流(liu)从(cong)干电(dian)(dian)(dian)池的(de)正极出发，经过(guo)电(dian)(dian)(dian)线、小电(dian)(dian)(dian)珠、电(dian)(dian)(dian)键(jian)，从(cong)干电(dian)(dian)(dian)池的(de)负极，流(liu)回到电(dian)(dian)(dian)池里去。

室内照明电路的电源是(shi)供电系统供给的。有两根(gen)导线(xian)，一(yi)(yi)根(gen)是(shi)火线(xian)，另一(yi)(yi)根(gen)是(shi)地线(xian)。安装(zhuang)都(dou)有一(yi)(yi)定(ding)的规格，开(kai)关要与火线(xian)连接。

在同一(yi)(yi)(yi)(yi)电(dian)(dian)(dian)路(lu)中常有好几种电(dian)(dian)(dian)器(qi)(qi)，连(lian)接的(de)(de)方法一(yi)(yi)(yi)(yi)般(ban)有串(chuan)联(lian)和并联(lian)。串(chuan)联(lian)就是(shi)把所有的(de)(de)电(dian)(dian)(dian)器(qi)(qi)按次序依次接入电(dian)(dian)(dian)路(lu)中。用串(chuan)联(lian)方法安(an)装(zhuang)的(de)(de)电(dian)(dian)(dian)器(qi)(qi)，切(qie)断一(yi)(yi)(yi)(yi)个(ge)(ge)(ge)电(dian)(dian)(dian)器(qi)(qi)，其它电(dian)(dian)(dian)器(qi)(qi)也同时跟(gen)着一(yi)(yi)(yi)(yi)起(qi)停止(zhi)使(shi)用。并联(lian)就是(shi)把所有的(de)(de)电(dian)(dian)(dian)器(qi)(qi)的(de)(de)两端(duan)分别连(lian)接在一(yi)(yi)(yi)(yi)起(qi)，再(zai)接入电(dian)(dian)(dian)路(lu)中。用并联(lian)方法安(an)装(zhuang)的(de)(de)电(dian)(dian)(dian)器(qi)(qi)，切(qie)断一(yi)(yi)(yi)(yi)个(ge)(ge)(ge)支路(lu)的(de)(de)开关，这个(ge)(ge)(ge)支路(lu)上的(de)(de)电(dian)(dian)(dian)器(qi)(qi)停止(zhi)使(shi)用，但不(bu)妨碍另一(yi)(yi)(yi)(yi)个(ge)(ge)(ge)支路(lu)的(de)(de)电(dian)(dian)(dian)器(qi)(qi)正常使(shi)用。我们室内用的(de)(de)电(dian)(dian)(dian)路(lu)一(yi)(yi)(yi)(yi)般(ban)都是(shi)并联(lian)连(lian)接。

1.第一段运(yun)用了哪些说明方法？各举一例。（20分）

答：

2.概括第二段的大意(yi)。

答：

3.用(yong)横线标出第三段的中(zhong)心句。

4.第(di)三段(duan)用(yong)了哪(na)些说明方法(fa)？各举一例。

答：

5.用本文的说明对象给这篇(pian)文章命一个标题。