在“測(cè)量小燈泡額定功率”實(shí)驗(yàn)中,小燈泡的額定電壓U額=2.5V.
(1)圖甲是測(cè)量小燈泡額定功率的實(shí)物電路圖,圖中有一根線連接錯(cuò)誤,請(qǐng)?jiān)谶@根線上打“×”,并在圖中改正___.
![](http://thumb.zyjl.cn/pic6/res/CZWL/web/STSource/2020031107415292356660/SYS202003110742090170587807_ST/SYS202003110742090170587807_ST.001.png)
(2)閉合開關(guān)前,滑片P應(yīng)位于________(選填“A”或“B”)端.
(3)閉合開關(guān),移動(dòng)滑片P直到電壓表示數(shù)為2.5V,此時(shí)電流表示數(shù)如圖乙所示,則小燈泡的額定功率為________ W.
![](http://thumb.zyjl.cn/pic6/res/CZWL/web/STSource/2020031107415292356660/SYS202003110742090170587807_ST/SYS202003110742090170587807_ST.002.png)
(4)小華設(shè)計(jì)了如圖丙所示的電路也完成了該實(shí)驗(yàn),請(qǐng)完成下列填空(電源電壓不變,R1和R2為滑動(dòng)變阻器,R2的最大電阻為R0). ①只閉合開關(guān)________,調(diào)節(jié)R2 , 使電壓表的示數(shù)為2.5V;
②只閉合開關(guān)________,調(diào)節(jié)________,使電壓表的示數(shù)仍為2.5V;
③接著將R2的滑片P調(diào)至最左端,記下電壓表的示數(shù)為U1;再將R2的滑片P調(diào)至最右端,記下電壓表的示數(shù)為U2 , 則小燈泡額定功率的表達(dá)式P額=________(用U額、R0、U1、U2表示).
![](http://thumb.zyjl.cn/pic6/res/CZWL/web/STSource/2020031107415292356660/SYS202003110742090170587807_ST/SYS202003110742090170587807_ST.003.png)