Q:    Find the source current I_s in the given figure.

Solution:

We need to calculate the source current. The value of voltage across 3kΩ resistor is 12V. Therefore the current (I) passing through it, is

                                                                        I = V/R

                                                                            = 12/3k = 4mA

The similar current is passing through the series combination of 3kΩ & 9kΩ resistor. 3kΩ is in series along 9kΩ & 2kΩ is in series along 4kΩ, therefore

Now through current division rule the source current will be as

                                                   I = (6k/ (12k +6k)) I_s = (18k/6k) 4mA   =12mA Ans.