（2010?南通模拟）如图（a）所示的电路中，电源电压保持不变，闭合开关S后，滑动变阻器的滑片P由a端移动 （2004?淮安）如图a所示的电路中，电源电压保持不变，闭合...
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（1）R与滑动变阻器串联，电压表V测R两端的电压，电压表V1测滑动变阻器两端的电压．当p滑至a端时，Rp=0，电路中最大电流，I=1.5A，R两端的电压等于电源电压，∴U=12V
（2）由（1）可得：
R＝
| U |
| I |
| 12V |
| 1.5A |
当p滑至b端时，变阻器电阻R1最大，电路中电流最小：I小=0.5A，即：I小＝
| U |
| R+R1 |
| 12V |
| 8Ω+R1 |
所以：R1=16Ω
（3）当p滑至a时，U1=0V，当p滑至b时，U1?=I1R1=0.5A×16Ω=8V
所以，电压表V1示数的变化范围为0～8V
答：（1）电源的电压为12V；
（2）滑动变阻器的最大阻值为16Ω；
（3）电压表V1示数的变化范围0～8V．
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