Question

某同學(xué)設(shè)計(jì)了如圖所示的電路，該電路能夠測(cè)量電源E的電動(dòng)勢(shì)和內(nèi)電阻r，E′是輔助電源．A、B兩點(diǎn)間有一靈敏電流計(jì)G．                                                                                                            

（1）補(bǔ)充下列實(shí)驗(yàn)步驟：                                                                                               

①閉合開(kāi)關(guān)S₁、S₂，                                                使得靈敏電流計(jì)的示數(shù)為零，這時(shí)，A、B兩點(diǎn)U_A、U_B的關(guān)系是U_A                                                         U_B，即A、B相當(dāng)于同一點(diǎn)，讀出電流表和電壓表的示數(shù)I₁和U₁，其中I₁就是通過(guò)電源E的電流．                                      

②改變滑動(dòng)變阻器R、R′的阻值，重新使得              ，讀出                                         ．

（2）寫出步驟①②對(duì)應(yīng)的方程式及電動(dòng)勢(shì)和內(nèi)電阻的表達(dá)式              ；                         ，                     

                                                                                               

                                                                                                                                       

Answer 1

（1）①調(diào)節(jié)R和R′；②靈敏電流計(jì)示數(shù)為零，電流表和電壓表的示數(shù)I₂和U₂

（2）E=I₁r+U₁ E=I₂r+U₂，U₁+，