0.02A*10Ω=0.2v
(10A-0.02A)×0.03Ω=9.98*0.03=0.2994v
(0.2994-0.2)÷0.02=4.97Ω
应给表头串联4.97Ω的电阻,然后再并联上述的分流电阻才行