Knowing that I

_{1}= 100mA, I_{3}= 300mA,

U_{R2}= 10V, determine R_{2}.

So I tried it like this: we know that in parallel connection, the voltage stays the same so U_{R2} = U_{R1} = 10V. Then, R_{1} = U_{1} / I_{1} = 100 Ohm. Also, I_{3} = I_{2} + I_{1} so I_{2} = 0.3A – 0.1A = 0.2A and so R_{2} = 10 / 0.2 = 50 Ohm.

Is this correct? I'm trying to learn for the exam but something doesn't seem right to me here.

## Best Answer

Your answer is correct but your method too complicated. If you know I1 and I3, then the resistors R1 and R3 really don't matter. Apply Kirchoff's current law for I1, I2 and I3.