电学题解答.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,2012-12-7,#,R,1,R,2,A,V,V,1,2,B,如图所示，电源电压保持不变，电阻,R1,的阻值为,2,欧，闭合开关,S,后，当滑动变阻器的滑片,P,位于,A,点时，电压表,V1,的示数为,4V,，电压表,V2,的示数为,10V,当滑动变阻器的滑片,P,位于,B,点时，电压表,V1,的示数为,8V,，电压表,V2,的示数为,11V,。则电阻,R2,的阻值是,欧,当,P,在,A,点时,R,1,与,R,A,和,R,2,串联,后接入电路,电路中的总电阻,R=,R,1,+R,A,+R,2,R,1,R,2,A,V,V,1,2,B,p,电路中的,电流,I=U,/,R=U,/,(R,1,+R,A,+R,2,),R,1,=2,电压表,V1,测量的,R1,和,RA,的总电压,.,即有,:U,1,=I,(R,1,+R,A,),=U,(R,1,+R,A,),/,(R,1,+R,A,+R,2,),=4,则有,:,U,(2+R,A,),/,(2+R,A,+R,2,),=4,电路中,电压表,V2,测量的,R2,和,RA,的总电压,.,即有,:U,2,=I,(R,2,+R,A,),=U,(R,1,+R,A,),/,(R,1,+R,A,+R,2,),=10,则有,:,U,(R,2,+R,A,),/,(2+R,A,+R,2,),=10,式,式,联立,式,可解得,:,变形得,:,U,=4,(2+R,A,+R,2,),/,(2+R,A,),变形得,:,U,=10,(2+R,A,+R,2,),/,(R,2,+R,A,),设电源电压为,U,变阻器的,P,在,A,点时连入电路的电阻为,R,A,在,B,点时连入电路中的电阻为,R,B,10,(2+R,A,+R,2,),/,(R,2,+R,A,),=4,(2+R,A,+R,2,),/,(2+R,A,),5,/,(R,2,+R,A,),=2,/,(2+R,A,),约去公约数,2,(2+R,A,+R,2,),可得,:,由两,外项,之积等于两,内项,之积,:,5(2+R,A,),=,2,(R,2,+R,A,),整理后可得,:,10+5 R,A,=,2,R,2,+2R,A,移项合并同类项整理后可得,:,3 R,A,=,2,R,2,-10,R,A,=,最后可得,:,式,将,式代入,或,式,可解得,:,U,=4,(2+,R,A,+R,2,),/,(2+,R,A,)=,分子分母同乘以,3,去分母可得,:,U=,移项合并同类项整理后可得,:,U=,化简后可得,:,U=,式,当,P,在,B,点时,R,1,与,R,A,和,R,2,串联,后接入电路,电路中的总电阻,R=R,1,+R,B,+R,2,R,1,R,2,A,V,V,1,2,B,p,电路中的,电流,I=U,/,R=U,/,(R,1,+R,B,+R,2,),R,1,=2,电压表,V1,测量的,R1,和,RB,的总电压,.,即有,:U,1,=I,(,(R,1,+R,B,),=U,(R,1,+R,B,),/,(R,1,+R,B,+R,2,)=8,则有,:,U,(2+R,B,),/,(2+R,B,+R,2,)=4,电压表,V,2,测量的,R,2,和,R,B,的总电压,.,即有,:U,2,=I,(R,2,+R,B,),=U,(R,1,+R,B,),/,(R,1,+R,B,+R,2,)=11,则有,:,U,(R,2,+R,B,),/,(2+R,B,+R,2,)=11,式,式,联立,式,可解得,:,变形得,:,U,=8,(2+R,B,+R,2,),/,(2+R,B,),变形得,:,U,=10,(2+R,B,+R,2,)/,(R,2,+R,B,),设电源电压为,U,变阻器的,P,在,A,点时连入电路的电阻为,R,A,在,B,点时连入电路中的电阻为,R,B,11,(2+R,B,+R,2,),/,(R,2,+R,B,),=8,(2+R,A,+R,2,),/,(R,2,+R,B,),11,/,(R,2,+R,B,),=8,/,(2+R,B,),约去公约数,(2+R,B,+R,2,),可得,:,由两,外项,之积等于两,内项,之积,:,11(2+R,B,),=,8,(R,2,+R,B,),整理后可得,:,22+11 R,B,=,8,R,2,+8R,B,移项合并同类项整理后可得,:,3 R,B,=,8,R,2,-22,R,B,=,最后可得,:,式,将,式代入,或,式,可解得,:,U,=8,(2+,R,B,+R,2,),/,(2+,R,B,)=,分子分母同乘以,3,去分母可得,:,U=,移项合并同类项整理后可得,:,U=,化简后可得,:,U=,式,联立,式,可得,:,U=,U=,=,去分母可得,:10R,2,-8 =11R,2,-16,移项整理可得,:R,2,=,8,