Determine the power of each source.
a) The current source keeps the current of the loop and the voltage source keeps the voltage across the current source as shown below.
For the voltage source the current enters from the positive terminal. Therefore, the passive sign convention should be used to find the sign of power:
For the current source, the current leaves from the positive terminal. Hence, the active sign convention should be used:
b) Similarily, the voltage across the current source and the currentpassing through thevoltage source can be easily determined by voltage and current sources, respectively:
For this problem, the current enters to the voltage source from the negative terminal. Thus, the active sign convention should be used: