theBEAST said:
Homework Statement
I am somewhat confused about when you can add parallel current sources:
Are the sources in the diagram I drew - A - in parallel? To me they look like they are but I am not sure... Is there an easy way to visualize these problems?
Your diagram has the power supply missing, but assuming it is meant to be on the right - as in the original - you cannot just combine the two like you could in the first.
To redraw, I could imagine the V- is pulled ot to the extreme left, while the V+ is pulled to the right, then each component arranged horizontal.
In case 1:
I would then have:
V- on the left, with the wire from it splitting into two branches.
The bottom branch has the 8kΩ resistor then meets a coming together leading to the V+ on the right.
The upper branch first splits into 3 branches - with a diode, a 4kΩ and a diode on those branches. those branches come back together to a single wire which passes through a 4kΩ resistor before rejoining the bottom branch and thence to V+
The three components, shown on the left of the original circuit diagram, and now clearly seen to be in parallel with each other. Through that three-some flows 2 mA, 2mA plus what ever gets through the 4kΩ resistor - with all that current going on to flow through the second 4kΩ resistor. That mans the 2 x 2mA currents could be considered as a single 4mA current.
In case 2, if you re-draw it in a similar way the circuit would appear as 3 overall branches, with the top branch splitting into two before rejoining and passing through a 4kΩ resistor.
In that case the two diodes are completely separated, and you cannot add the 2 x 2mA to form a single 4mA