Electrical – Calculating power absorbed by each element

What, I think, is being asked is for you to find the Thevenin equivalent of the circuit seen by the current source.

In other words, remove the current source and then find:

(1) the open circuit voltage across the port where the current source was formally connected

(2) the equivalent resistance looking into that port.

For example, consider the following circuit:

^{simulate this circuit – Schematic created using CircuitLab}

The Thevenin equivalent across (or seen by) the current source is

^{simulate this circuit}

where

\$R_{th} = R_1||R_2 \$

\$V_{th} = V_1 \dfrac{R_1}{R_1 + R_2} \$

You don't need meshes. Just calculate everything one source at a time, while keeping the other sources zeroed out (i.e. a voltage source is replaced with a wire, and a current source is replaced with an open (cut) circuit). Then sum the results from each source.

So in this case, the voltage source would see nothing but four resistors in series, and both current sources would see (different sets of) 2 series resistors connected in parallel with 2 other series resistors. Hopefully this helps you see how to "zero" the sources.

I'm not familiar with MIT's Circuit Sandbox, but it shouldn't matter where you put the ground since you just need to check the current flowing in different places - so just pick a spot and call it ground!