As shown in the circuit , the value of the current source is has been known: If the internal resistance of the voltmeter is infinite, what is the reading of the voltmeter U2=______? Choose A or B. We have the model of the ideal transformer.In the model of ideal transformer, there is a simple real algebraic relation between U1 and U2,that is U1/U2=N1/N2.Between I1 and I2 there is also a simple real algebraic relation,that is I2/I1=N1/N2.Turns ratio of N1 and N2 is 2, if the secondary siede impedence Z is equal to 3+j4 Ω , the impedence in the primary side Zeq is equal to Zeq=[(N1/N2 ) .^2]*Z.But ,in this picture, we can see that on the secondary side , Z= ,so Zeq= , I2=0, U1/U2=N1/N2=2.Seeing from the primary side, the ideal transformer makes the the iuput impedecne should be 10 Ω only. The effective current value is 4 A. So U1=10*4=40V,U2=________.