Current Divider Example # 3: Finding Value of Unknown Resistor

A current source of 100 mA powers two parallel resistors, the first resistor is of 30 Ω and it receives 60 mA current, Find the value of the second resistor.

Solution: R_1 dissipates the 60 mA, the remaining 40 mA current will pass through R_2.

From the Ohm's law, the voltage across 30-ohm resistor is 1.8 V.

R_1 and R_2 join in parallel and both have the same voltage across them.

V_R_2 = 1.8 V,

Using the Ohm's law R2 = V_R2/I_R2 = 1.8 V / 40 mA

R2 = 45 ohm

So 45 ohm is the right answer.