(20 14? Nanjing) As shown in the figure, the power supply voltage is constant, r1= 20Ω, the switch S is closed, the switch S 1 is turned off, and the current is expressed as 0.3A；; If S 1 closes again

(20 14? Nanjing) As shown in the figure, the power supply voltage is constant, r1= 20Ω, the switch S is closed, the switch S 1 is turned off, and the current is expressed as 0.3A；; If S 1 closes again. (1) When S is closed and S 1 is open, the circuit is a simple circuit of R 1; According to I=UR, power supply voltage: u = u1= I1r1= 0.3a× 20ω = 6V;

(2) If S 1 is closed again, two resistors are connected in parallel, U2=U=6V, and the current represents the current of R2 branch, then I2 = 0.2A；;

According to I=UR, R2 = u2R2 = 6v0.2a = 30ω.

So the answer is: 6; 30.