题目　组成串联电路和并联电路 ,所给器材有 :定值电阻Ｒ1 、Ｒ2 、Ｒ3,电源 (电压不变 )和开关各一个 ,导线若干 .每次组成电路时 ,可以三个电阻都用或任意选用两个 .对符合以上要求的所有的各种电路 ,用电流表来测量通过各个电阻的电流和干路电流 ,用电压表来测量各个电阻两? The subject consists of a series circuit and a parallel circuit. The devices given are: fixed-value resistors R1, R2, R3, a power supply (invariable voltage) and a switch each, several wires. Each time a circuit is formed, three resistors can be used or arbitrary Choose two. For all the various circuits that meet the above requirements, use an ammeter to measure the current through each resistor and the trunk current. Use a voltmeter to measure each resistance.