某毫安表的量程为I0=50mA，内阻为r0=50Ω，其表盘刻度线已模糊不清，要重新通过测量来刻画出从零到满刻度的刻度值，备有下列器材：A．待测毫安表mAB．直流电源E（电动势3V，内阻可
| A | 1 |
| r | 1 |
| A | 1 |
| r | 0 |
| R | 3 |
（根据方案二应有：I
| r | 0 |
| I | 1 |
| (r | 1 |
| +R | 3 |
| ||||||
|
其中
| I | 1 |
| A | 1 |
| r | 1 |
| A | 1 |
| r | 0 |
| R | 3 |
故答案为：①ABXEGI
②如图
③
| ||||
|
| A | 1 |
| r | 1 |
| A | 1 |
| r | 0 |
| R | 3 |
| r | 0 |
| I | 1 |
| (r | 1 |
| +R | 3 |
| ||||||
|
| I | 1 |
| A | 1 |
| r | 1 |
| A | 1 |
| r | 0 |
| R | 3 |
| ||||
|
