Giải Ta có \(I = {I_1} + {I_2} + ... + {I_n}\)\({{{U_{BA}} + {\xi _b}} \over {{r_b}}} = {{{U_{BA}} + \xi } \over r} + {{{U_{BA}} + \xi } \over r} + ... + {{{U_{BA}} + \xi } \over r}\)\({{{U_{BA}} + {\xi _b}} \over {{r_b}}} = n{{{U_{BA}} + \xi } \over r} = {{{U_{BA}} + \xi } \over {{r \over n}}}\)Đồng nhất suy ra: \({\xi _b} = \xi ;\,{r_b} = {r \over n}\)
